Filareti Tsalakanidou

Symeon Papadopoulos

Vasileios Mezaris

Ioannis Kompatsiaris

Birgit Gray

Danae Tsabouraki

Maritini Kalogerini

Fulvio Negro

Maurizio Montagnuolo

Jesse De Vos

Philo Van Kemenade

Daniele Gravina

Rémi Mignot

Alexey Ozerov

Francois Schnitzler

Artur Garcia-Saez

Georgios N Yannakakis

Antonios Liapis

Georgi Kostadinov

The AI4Media Project: Use of Next-Generation Artificial Intelligence Technologies for Media Sector Applications

Keywords: Artificial Intelligence, Media, Democracy, Society, Use Cases, Social Media, Content Automation, Vision, Journalism, Co-creation, Gaming

des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

1

Artificial Intelligence in the Service of Media, Society and Democracy: Current Challenges & Opportunities

Following a series of breakthroughs in the field of Artificial Intelligence (AI), new technologies are emerging which are ushering a wave of innovations in all aspects of business and society, across industry sectors such as transportation, health or finance, for global goals such as fighting climate change, also impacting the media industry, journalism and politics [START_REF] Russel | Artificial Intelligence: A Modern Approach[END_REF]. In all these facets of economic and social life, AI is disrupting existing practices and creates opportunities. The exploitation of these opportunities brings significant socio-economic changes that necessitate a focus on issues of trust, ethics and accountability, besides the pursuit of technological excellence and financial profit. This human-centric and trustworthy ethical brand of AI is particularly relevant to the media sector. Digital media permeates most aspects of human and social activity and is intertwined with information exchange and knowledge transfer. Machine vision and visual content understanding were some of the first fields to exhibit significant breakthroughs in the evolution of AI, including advances in audio/music analysis and generation, text and language analysis, and modeling of social trends. The media market is already benefiting from AI-based support across the value chain: for media newsgathering, production, distribution, and delivery as well as audience analysis. This includes a range of tools and services for processes such as information analysis, content creation, media editing, content optimisation, audience preference analysis, and recommender systems [START_REF]AI and the Media: Too Hot, Too Cold, Just Right? A Mapping of Artificial Intelligence Applications[END_REF].

Furthermore, it has become apparent that society and politics are increasingly affected by AI developments. There is strong concern that the combination of the power held by the major, globally operating social media platforms and the large-scale automation capabilities associated with these platforms offered by AI technology could prove detrimental to individuals, society and democracy [START_REF] Sunstein | # Republic: Divided democracy in the age of social media[END_REF]. For instance, AIpowered bot collectives were found to have played an important role in shaping the results of US Elections in 2016 and the Brexit referendum [START_REF] Smialek | Twitter Bots Helped Trump and Brexit Win, Economic Study Says, Bloomberg article[END_REF] while the recent advent of synthetic media technology is posing new risks to citizens' trust in online content.

AI technologies are expected to disrupt the media industry through advances in content synthesis, analysis, and distribution, but also by offering new deeper insights into the complex and rapidly evolving social processes that unfold online and offline by sensing citizen activities, interests and opinions [START_REF]AI and the Media: Too Hot, Too Cold, Just Right? A Mapping of Artificial Intelligence Applications[END_REF]. AI technology could help shape the democratic role of the media by enabling new ways of being informed, of deliberation, political participation, and decision making. In addition, AI technologies could support the relationship between media providers and their audiences, helping to align with the needs of media users and citizens. The use of AI can also cut down operating costs and ultimately free up resources for more in-depth and quality journalism. In addition, the use of AI can also create opportunities for the better realization of public values, such as media diversity, freedom of expression, and inclusiveness.

Motivated by the challenges, risks and opportunities that a wider use of AI brings to the media sector and society, the EU-funded AI4Media project [START_REF]AI4Media Website[END_REF] aspires to i) deliver the next generation of core AI technologies, ii) ensure the embedding of ethi-cal and trustworthy AI into future AI deployments, and iii) reimagine AI as a humancentered, trusted and beneficial enabling technology for media and society.

AI4Media aims to advance the AI state-of-the-art in four key technology areas, with a view to unify a currently fragmented landscape of media related AI and offer solutions for the ever-growing needs and challenges of media organizations:

 New learning paradigms and distributed AI: AI models that adapt and learn on-thefly, models that teach each other, algorithms that learn from limited data; Distributed AI and AI systems operating on the Edge.  Explainability, robustness and privacy in AI: Federated learning and privacyenhancing technologies ensuring data privacy; Technologies that protect information systems from malicious attacks and increase robustness; Approaches for evaluation, systematization, and explainability of AI.  Content-centered AI: Multimedia metadata extraction, summarization, and clustering; Automatic audiovisual content generation and enhancement; Linguistic analysis; Learning with sparse data and transfer learning.  Human-and Society-centered AI: Technologies for multimedia manipulation detection; Political opinion mining, disinformation detection, and local news detection; User perception measurement algorithms for personalization and bias detection; Privacy-preserving content recommendation.

The developed technologies will be tested in the context of seven industrial use cases that focus on the media sector, with relevance for both society and the economy. They cover different forms of media, such as digital content, broadcast video, film, audio, music, games, and virtual environments. Content areas include news stories, social media, media archives, and user-generated content. The use cases also address a variety of societal and democracy related topics such as disinformation, public discourse, media moderation, consumer privacy, creativity, and human-machine interaction. The seven use cases will be realized through close collaboration between AI researchers and European media organizations or content related companies.

The rest of the paper is organized as follows: Section 2 discusses the AI technologies explored in AI4Media that focus on the media sector. Section 3 presents the seven AI4Media use cases. Finally, section 4 draws the conclusions.

AI technologies for the Media Sector

AI4Media will conduct research in cutting-edge AI areas, focusing on tools and applications for the Media Industry. In the following, we briefly discuss the spectrum of AI technologies that will be examined in the context of the project and the use cases. New learning paradigms. The AI explosion was initially spearheaded by Convolutional Neural Networks (CNNs) and Recurrent Neural Networks (RNNs) applied to well-known classification tasks. Building on this, we focus on developing faster and more accurate learning models by examining: techniques for lifelong learning to allow updating system capabilities without forgetting past knowledge [START_REF] Parisi | Continual lifelong learning with neural networks: A review[END_REF]; new spaces and operators for unsupervised manifold learning to exploit non-annotated data; trans-fer learning to allow reusing models trained for different tasks [START_REF] Bengio | Curriculum learning[END_REF]; transfer neural architecture search to find suitable DNN architectures fast by leveraging past experience in different datasets [START_REF] Wistuba | XferNAS: Transfer Neural Architecture Search[END_REF]; and deep Quality Diversity methods for DNNs to improve quality and diversity of generated outcomes in gaming [START_REF] Gravina | Quality Diversity through surprise[END_REF]. We leverage Quantum architectures and test the efficiency of Quantum-inspired ML algorithms dealing with large datasets. We also move AI from centralized cloud architectures to networks of heterogeneous devices, to allow lightweight devices sitting on the Cloud Edge to run their own DNN models [START_REF] Szegedy | Going deeper with convolutions[END_REF]. In this direction, we explore distributed learning and decentralized graph mining.

Trustworthy AI. To ensure trustworthy AI for media applications, AI robustness, explainability, privacy and fairness are explored. We focus on enhancing system resilience towards adversarial attacks like poisoning or evasion [START_REF] Yuan | Adversarial examples: Attacks and defenses for deep learning[END_REF]; improving AI interpretability [12] with regard to the use of DNNs for tasks like deepfake detection; improving the privacy aspect of recommendation systems by combining de-centralized methods for federated learning [START_REF] Jalalirad | A Simple and Efficient Federated Recommender System[END_REF], differential privacy and encryption; and improving fairness through detection and mitigation of bias in recommendation systems [START_REF] Ntoutsi | Bias in data-driven artificial intelligence systems -An introductory survey[END_REF]. These contributions will be supplemented by a new benchmarking framework aiming to evaluate effectiveness and reproducibility of AI systems.

Multimedia content analysis and creation. The aim is to provide improvements on the state of the art, such as development of better automatic video summarization algorithms for news agencies based on Generative Adversarial Networks (GANs) [START_REF] Apostolidis | A Stepwise, Labelbased Approach for Improving the Adversarial Training in Unsupervised Video Summarization[END_REF] and on combination of knowledge representation and deep learning; and to design better audio generation algorithms for games, exploiting DNNs and domain-specific knowledge for music annotation and audio analysis [START_REF] Pons | End-to-end learning for music audio tagging at scale[END_REF]. In addition, we explore vision-based DNNs for automatic online cinematography based on UAV footage [START_REF] Nägeli | Real-time planning for automated multi-view drone cinematography[END_REF], while also developing image enhancement techniques for 360 videos, thermal imagery, depth, etc. We also improve visual detection tasks by using GANs and 3D virtual world simulators to tackle data scarcity [START_REF] Reed | Learning what and where to draw[END_REF]. Finally, we improve Word Embeddings for NLP algorithms [START_REF] Mikolov | Distributed representations of words and phrases and their compositionality[END_REF] to provide efficient multi-language models.

Human-centered AI. Online platforms have become a central source of information, shaping the democratic debate and society [START_REF] Sunstein | # Republic: Divided democracy in the age of social media[END_REF]. To support journalists in providing trustworthy information and citizens in being adequately informed outside of filter bubbles, AI4Media: tackles multimedia content manipulation (deepfakes) by combining text verification based on graph mining [START_REF] Zellers | Defending Against Neural Fake News[END_REF], audio analysis, and video analysis based on extended GANs [START_REF] Mercier | Detecting Manipulations in Video[END_REF] and novel video pre-processing approaches [START_REF] Charitidis | Investigating the Impact of Pre-processing and Prediction Aggregation on the DeepFake Detection Task[END_REF]; promotes healthy political debate by including diversity and novelty in recommender systems to avoid over-personalisation [START_REF] Kaminskas | Diversity, serendipity, novelty, and coverage: a survey and empirical analysis of beyond-accuracy objectives in recommender systems[END_REF], and by modeling disinformation and political polarization in national and local scale; and finally, analyzes user perception of social media through a combination of user studies and content analysis [START_REF] Koelstra | Fusion of facial expressions and EEG for implicit affective tagging[END_REF].

The AI4Media Use Cases

AI4Media has designed seven use cases that demonstrate the use of AI in the media industry, including aspects of human-centric, ethical and trustworthy AI (see Fig. 1).

The AI4Media use cases (UC) are inspired by market needs, emerging opportunities, and a range of industry challenges, and they highlight how AI applies throughout the media and content value chain and how different types of media players aim to address user and business needs with novel AI solutions.

The use cases deal with a broad range of media processes that will be optimized and enhanced by the application of state-of-the-art AI technologies. The industry partners gather a set of user requirements for new AI functionalities with a view to upgrade available tools already used by the media sector with AI features developed by the project (see section 2). In the following, we present the seven use cases.

UC1: AI for Social Media and Against Disinformation

While disinformation activities and the volume of related verification work increase, the workflow for verifying digital content items and detecting disinformation remains complex, time-consuming and often requires specialists. The current generation of support tools lack functions for identifying the most recent forms of manipulated content and easily understanding disinformation patterns in social media. In addition, technologies used for content manipulation and disinformation have become more advanced, also involving synthetic media. There is a need for upgraded, easy-to-use tools with trusted AI functions, as more journalists and other researchers will be involved in content verification and disinformation detection tasks. In order to ensure acceptance of AI-based tools and the feasibility of their implementation, users need to judge aspects of trustworthiness with regard to machine-generated results and predictions, such as Explainability, Bias Mitigation, Robustness or Ethical Compliance. This use case from Deutsche Welle and ATC leverages AI technologies to improve support tools used by journalists and fact-checking experts for digital content verification and disinformation detection. New AI-based features will be made available within two existing journalism tools: Truly Media [START_REF]Truly Media homepage[END_REF] (web-based platform for collaborative verification) and TruthNest [26] (Twitter analytics and bot detection tool).

Two topics are covered: i) verification of content from social media with a focus on synthetic media detection, and ii) detection of communication narratives and patterns that are related to disinformation. Another aspect is the exploration of Trustworthy AI in relation to these topics and the specific needs of media organisations.

The detection and verification of synthetic media refers to both synthetically generated media items and synthetic elements within media items. This provides contextual information for the verification process, helping journalists and researchers to understand specific manipulation activities. The more advanced synthetic media be-comes, the more difficult and time-consuming it will be to detect it. While there are useful and entertaining applications for synthetic media, it is also used for targeted, malicious disinformation. Synthetic media items misused for disinformation purposes are colloquially known as Deepfakes [START_REF] Mirsky | The creation and detection of deepfakes: A survey[END_REF]. All types of content can be synthetically generated (or manipulated): text, images, audio, video and elements within AR/VR experiences. Synthetic Characters can be either fictional or with high levels of likeness to a person, its voice and personality.

Another goal is to provide AI-based tools for better understanding communication patterns in social media that are related to disinformation. This includes the detection of topical disinformation campaigns or stories, which may entail false or distorted information. The latter can emerge dynamically, or be steered by certain social media actors and networked communities in order to achieve a specific objective.

We address these challenges by collecting specific user needs in the area of content verification and disinformation detection that might be solved by advanced AI functionalities, including needs for associated Trustworthy AI features. Once respective AI tools have been developed in AI4Media, they will be tested against end user and business needs within Truly Media and TruthNest (see Fig. 2).

Fig. 2. AI technologies for content verification and disinformation detection developed in

AI4Media will be integrated in existing journalism tools like Truly Media.

UC2: AI for News -The Smart News Assistant

Journalists face a challenging environment where the amount of incoming content is ever increasing while the need to publish news as fast as possible is extremely pressing. On top of that, journalists need to ensure that published content is trustworthy and relevant for its audience. The use case focuses on the concept of a Smart News Assistant, i.e. a tool that will support journalists in the creation of news stories by providing a variety of AI-enabled functionalities for story production and development, story curation and publication, and audience engagement. Story development will be facilitated by providing automatic story suggestions based on analytics of past audience engagement and trend detection in social media, as well as by providing real-time suggestions during article preparation, e.g. suggest-ing relevant articles or video content from news archives and warning about fake news. Functionalities for automated news articles summaries, automated article indexing and annotation for easier search, automated content curation and adaptation to different audience needs, and personalised news experiences based on past behaviour of news consumers will be supported to enhance story curation. Finally, semiautomated moderation of online discussions about news articles, including polarisation detection and classification of disagreements, and automatic management of audience feedback will be supported to facilitate audience interaction and engagement.

UC3: AI for High Quality Video Production & Content Automation

This use case aims at supporting broadcasters' newsrooms (and in general information and entertainment production) in reporting unexpected events like natural disasters (e.g., floods, earthquakes). Generally, whenever similar events occur, newsrooms need to readily publish and update fresh news in a very short timeframe. It is evident that the "time" variable plays a crucial role: providing and getting news on time can make all the difference and the entire production process is stressed. Together, content quality and reliability must always be properly and readily verified before flowing into the production chain. AI4Media aims to broaden the horizons along three perspectives involved in such just-in-time, high-quality production process (Fig. 3). First, timely coverage of unexpected events must be ensured. Several tools for professional news search and filtering are available, but they lack in providing new and engaging information as soon as an event occurs. However, auxiliary sources (e.g., social media and video sharing platforms) provide a plethora of information such as the nature of the disaster, affected people's emotions and relief efforts. Unfortunately, that content cannot be used indiscriminately due to e.g., quality, privacy and reliability issues. AI tools for content quality enhancement (e.g., denoising, dehazing, inpainting), privacy protection (e.g., identity obfuscation) and manipulation detection are the key to overcome such obstacles. Furthermore, AI computer vision technologies can speed up the creation of metadata, e.g., descriptive information about actions, places and things identifiable within the content, making it easier to be searched.

Second, broadcaster's archives are a valuable source of information about how the landscape was in the past. However, archive material might be impaired and inadequately documented. Thus, appropriate AI-based technologies are needed for video restoration (e.g., artifacts reduction, colourisation) and metadata extraction (e.g., image and video captioning). Furthermore, drone technology can provide unprecedented viewing experiences, e.g., by gathering data from inaccessible or arduous areas. Archives and drones might work in synergy and even amplify each other's results. Archive material might help in pre-setting operational drone's parameters (e.g., flight paths, altitude, speed) while drone camera footage might be used to assist the video restoration process, e.g., by providing chroma information for video colourisation.

At last, open data, professional newsgathering services and broadcast archives are the main data sources that could be used to enrich the storytelling with e.g., graphics, statistics and reports about past events related to the present one. AI may help the editorial staff analyse data and identify patterns and insights from these sources, thus reducing the effort for data scraping, aggregation, mining and transformation.

Results of AI4Media are expected to bring benefit along the whole value chain, including journalists, editorial staff, TV production, rights and privacy management departments, as well as media researchers. Finally, to the audience, who will enjoy always new, modern, original and high-quality content. Fig. 3. AI4Media aims to empower the whole news production process: from news analysis to high-quality and impactful content creation.

UC4: AI for Social Sciences and Humanities

Scholars from the humanities and social sciences have been adopting digital methods into their respective fields. Large, publicly accessible datasets allow researchers to distill trends beyond individual occurrences of media phenomena. This use case provides researchers (and by extension investigative journalists) with practical methods to sift, connect and analyze various data and media collections in search of factual responses to broad societal research questions. Our aim is to provide the AI-based tools that facilitate identification of patterns or new research questions in aggregated, multi-modal collections. Based on the AI tools, we envision an infrastructure that will facilitate gathering and preparation of data to support macro-level analysis, e.g. the role of political and gender bias in media programs, and micro-level analysis, e.g. close reading of specific programs, bias effects of speaker selection, and topic presentation. This includes the use of Computer Vision analysis and Natural Language Processing, but goes beyond detection of individual features, to equip researchers with reliable and explainable analyses and visualisations at aggregated levels. This use case focuses on issues of framing, representation and bias: topics of great interest to social sciences and humanities. However, the definition and operationalization of such complex societal issues is itself subject to debate. Scholars will develop their own understanding and identify more specific instances of these broad phenomena, e.g. the degree to which talk show hosts interrupt female versus male speakers, or the representation of violence in news channels covering a conflict. To facilitate such research with AI-based tools requires a great degree of flexibility and configurability. At the core, the tools should enable researchers to perform basic operations: detect entities in various modalities within large multi-modal datasets. But for example, what exactly the tools detect, which confidence scores for results are to be used and in which combinations entities should occur should be configurable by the researchers.

Finally, academic research has the highest standards when it comes to transparency of methodologies, fairness of representation in training sets and research reproducibility. Therefore, this use case will also evaluate the pre-conditional requirements for trustworthy AI-based tooling, which allows scholars to confidently deploy the tooling.

UC5: AI for Games

Over the past decade, the game industry has undergone drastic changes. There has been an increase of online games, digital distribution platforms, mobile and social games. Digital games are now services that rely on continuous developing and adding new content over the lifetime of the product in a winner-takes-all market. Before launch, optimizing a game for the market is crucial for success.

AI can provide a radically new approach for testing and optimizing games by letting developers test thousands of different configurations and cases instead of a few hundred or less. It can replace or augment existing practices by providing product evaluations faster than current methods. Additionally, AI may even provide methods for generating content automatically. The game industry is seeing an increased need for automation and improved efficiency. Finally, AI has the capacity to provide new gaming interactions. For the past decade, new control devices have been appearing with the aim to replace the traditional gamepad and provide more natural interaction.

To address these issues, this use case aims to advance the game testing, design and interaction through AI algorithmic innovations. It focuses on three topics: "Automated testing for Games": AI agents can be used to automatically detect bugs and glitches in video games by autonomously playing them and compiling test reports as human testers would do. Video game testing is a time-consuming process that traditionally has been entrusted to human testers. However, the future of the game market sees an increasing adoption of the game-as-a-service model, where new content has to be provided to players on a monthly basis. Therefore, quality assurance becomes a vital part of the game development cycle, as the new content produced has to be continuously tested.

"Improved music analysis and synthesis for Games": This aims to help developers to choose or conceive background music or sounds. In video games, the audio track has the role to strengthen the atmosphere of the present scene, and it has an impact on the emotion felt by the user. Developers can either choose music from a catalog or delegate this task to music composers or sound designers; but automatic AI tools may help, especially in the case of dynamic changes and procedural content generation.

"Natural game interaction through edge analysis of camera stream": With cloud gaming, end users can play games without dedicated hardware and directly interact with games running on the cloud and streamed to their home. A Smart TV equipped with a standard RGB camera coupled with AI on the edge will replace the gamepad for natural game interactions. The camera stream will be analyzed with AI models that dynamically adapt to the available resources and offloaded to the edge. The output of the analysis (e.g. human body detection, gestures) will be interpreted into game commands within stringent latency requirements and ensure the privacy of end users.

UC6: AI for Human Co-creation

Content generation is an exhaustive project often developed by a single or a reduced group of people. Many of the tasks involved require a high level of craftsmanship, and as such are available to a reduced number of experts after extensive training. In an era where content is consumed in a greedy manner by a gigantic audience, content creators face the necessity of novel tools to assist them in their creative process.

Music creation uses novel technologies in many ways, and a wide range of techniques are employed by composers routinely. These technologies have been evolving dramatically in recent years, with the introduction of AI into music generation. While this is a great opportunity for creators, it requires an increasing level of technical proficiency, out of reach of non-experts. A novel industry may emerge from this set of possibilities and requirements, giving each user a new personal experience of media addressed particularly to each taste. Authors need novel tools to develop their work and expand their creativity beyond the constraint of potentially automatized tasks.

Our goal is to reduce the gap between novel content creation techniques, in particular raw audio music, and artists/creators. The content may be also created and manipulated in real time according to external inputs. Tasks related to content creation are of different complexity, some of which are already performed in an automated way. In this context, novel tools may contribute to an efficient creation task, where efforts of the artist or creator are focused on deeply creative tasks, relying less on critical parts to be performed by an AI assistant.

The elaboration of creative assistants has a wide application to many different fields of creation. While visual arts are suited to the application of AI tools based on CNNs, recent developments on RNNs or similar techniques allow the efficient processing of music, speech, or video. In this context, the scope of interest of these techniques will soon cover the complete spectrum of content production.

This approach has potential impact in a broad range of disciplines, where the combination of data sources could add value. Beyond visual arts, we find many areas of human creation where language, image, sound, and other information are combined in complex ways, such as games. Tools to generate, modify and synchronise all these data sources are in need to automatically ensure quality and consistency of novel digital content. In this use case, we collaborate with music composers with previous experience with the use of AI to help us define new work methodologies and new ways of using AI in their creation. In particular, we focus on coupling raw audio CNNs with GANs trained with mood and emotional labels, lyrics, and other data extracted from music knowledge. Also, general purpose RNNs used in speech synthesis will be explored to process RAW audio from music tracks. The aim is to produce a novel way of content co-creation based on AI tools that reach a wide range of content.

UC7: AI for (re-)organisation and content moderation

Media companies have accumulated vast digital archives and collections of images and videos over the years. Since these collections have been gradually and iteratively built over time, often by different departments and units of media companies, they usually have little or no metadata such as tags, categories, and other types of annotations. This lack of coherent media asset organisation tailored to the media company business and services precludes the successful monetisation of these media assets and the creation and offering of new services. In addition, both big traditional media companies and more so digital media platforms combine in their collections both media content, created by these companies, but increasingly also User-Generated Content (UGC). Such hybrid media archives need advanced Content Moderation (CM) solutions, often working in real time to safeguard viewers and meet laws and regulations. To address these challenges, this use case utilizes several AI-enabled tools such as visual tagging, categorization, and content moderation to facilitate: a) Automated (re)organisation of large media collections of photos and video: Techniques for mapping existing taxonomies and ontologies used by media companies, to restructure them to more optimal ones, and training of specialized models for such companies using state-of-the-art CNNs for media asset categorisation will be used. The know-how of consortium partners with personal and enterprise photo collection organisation will be extended to mixed collections of photos and video.

b) Automated and human-in-the-loop moderation of user-generated media content: We will also use existing CM solutions that combine automated detection of diverse and customizable types of inappropriate content, such as weapons, drugs, nudity, pornography, etc. with a CM platform and option to add internal or external data teams to verify inappropriate content flagged by AI algorithms. As part of this use case, Imagga's CM platform [START_REF]Imagga Content Moderation Platform[END_REF] (Fig. 4) will be tested and further optimised with mixed and hybrid media collections and platforms where UGC can come both as standalone new visual content (photos, video) or as comments to existing media assets, such as films, news, etc. Additional focus will be on implementing a live-stream optimization module for optimizing costs and precision of automated real-time moderation. This will meet the growing demand of media companies to have scalable realtime content moderation to safeguard users and meet various regulations.

Additionally, the two demonstrators presented in this use case will be tested by target groups of real users from media companies in Living Lab trials, in order to validate their performance and help tailor them further to meet user requirements.

Conclusions

This paper offers an introduction to the AI4Media H2020 project. AI4Media aims to deliver the next generation of core AI technologies, including new AI learning paradigms and distributed AI; ensure the embedding of ethical and trustworthy AI into future AI deployments by exploring technologies for AI explainability, robustness and privacy; and reimagine AI as a human-centered, trusted and beneficial enabling technology for media and society. To this end, AI4Media introduces use cases focusing on the media sector that cover different forms of media and digital content while examining various societal and democracy related topics, such as disinformation, public discourse, media moderation, consumer privacy, creativity, and human-machine interaction. AI4Media is expected to build on the rich and diverse European media culture and its role in advancing public values, such as democracy, inclusiveness, political participation, diversity, and self-expression and thus contribute into strengthening Europe's position in the global AI research landscape.

Fig. 1 .

 1 Fig. 1. The AI4Media use cases.

Fig. 4 .

 4 Fig. 4. Imagga's CM platform will be enriched with AI functionalities delivered by AI4Media.

Acknowledgment. This work was supported by European Union's Horizon 2020 research and innovation programme under grant agreement No 951911 -AI4Media.


Mogens Laerke

Introduction

In a letter from 3 March 1715 to Gottfried Wilhelm Leibniz, the Abbé Castel de St. Pierre, member of the French Academy and author of a famous Projet pour rendre la paix perpétuelle en Europe (1713), exhorted the German polyhistor to undertake a similar project: "Why would you not, thus providing something entirely new on the project of European arbitration, write a work in German and in French that would be yours entirely; can the German Solon even omit to?" (Leibniz 1995: 49-50). 1 Leibniz, of course, never did. He already had a great many other things to do and only little time left to livehe died the following year, in November 1716. Moreover, like most of his contemporaries, he did not have enough intellectual regard for the French académicien to feel any obligation to heed his advice. 2 And yet St. Pierre had a point. It was not unwarranted to expect a work of this kind from the "German Solon." A lawyer by education, diplomat by trade, irenic theologian, court historian and political philosopher, Leibniz had spent a lifetime navigating the political and theological corridors of the Holy Roman Empire between Hanover, Vienna and Berlin. And it really was quite an understatement when Leibniz replied to St. Pierre that the topic was "not entirely outside [his] range of interests" (Leibniz 1988: 176-77). In fact, in terms of life experience and professional expertise, few were better situated than Leibniz to reflect on the 1 Unless otherwise indicated, translations are mine. Following standard usage, I refer to the Academy edition of Leibniz's writings [START_REF] Leibniz | Sämtliche Schriften und Briefe[END_REF] with the abbreviation "A," followed by the series and vol. number in roman numerals. The mention [ve] indicates a so-called Vorausedition, a preliminary, but incomplete edition made available by the Academy.) Most volumes are freely available online (http://www.leibniz-edition.de). 2 For Leibniz, St. Pierre's project was "a bit like Thomas More's Utopia" (Leibniz 1995: 23). Like Kant after him (Kant 1996: 309), Leibniz derided the vision of perpetual peace in Europe as an impossible "fiction" (Leibniz: 24), arguing that the only pax perpetua really possible was the kind inscribed on gravestones, "for the dead do not fight any longer: but the living are of another humor" (Leibniz 1988: 183;cf. 166). He thus joined many of St. Pierre's contemporary readers, like Nicolas Remond who, in April 1715, wrote to Leibniz that "the knowledge one has of the of the worker has done damage to the reputation of the work: it is believed that nothing good can come out of Abbé de St. Pierre's head" (Leibniz 1995: 52). See also Riley 1996: 244-45;Roldan 2011: 89-93. political history and future of Europe at the turn of the seventeenth century. His edition of ancient texts on international law, the 1693 Codex juris gentium diplomaticus, had gained him a reputation as one of the foremost experts of his time of the history of international law. Add to this an incredible mass of additional papers, mostly unpublished, written throughout his career, addressing European questions regarding everything from war and security, affairs of the court, church politics, education, commerce,3 and scientific collaboration.

It is difficult to point to any one of all these texts as expressing in full Leibniz's political vision of Europe. Certainly, the preface to the Codex and his commentary on the St.

Pierre's work, the so-called Observations sur le projet de paix perpétuelle (1715), contain many important parts of the puzzle, but one will not obtain any systematic idea without taking into account multiple other texts on political philosophy and real politics spanning over several decades, from the 1667 Nova methodus discendae docendaque jurisprudentiae (1667) and the Specimen demonstrationum politicarum pro eligendo rege polonorum (1669) to the Caesarinus fürstenerius (1677) and Mars Christianissimus (1683), and a host of other, less well-known political texts progressively brought to our attention by the still forthcoming volumes of the series IV of Leibniz's Sämtliche Schriften und Briefe, containing the political writings. 4 And, as is often the case when studying Leibniz's intellectual enterprises, by piecing together passages from a great many texts of different nature on different topics, written at different times on different occasions, it is possible to glean from them a reasonably unified vision of Europe as a political project.

The Balance of Europe

In the first place, Leibniz's vision for Europe forms a unity in virtue of the general societal goals it pursuesthe public good and the glory of Godand the intellectual ethics that governs it, which is essentially an ethics of reciprocity, moderation and Enlightenment (Laerke 2015: 47-106). Above all, it is united by the higher ideal of an "empire of reason": "The end of political science with regard to the doctrine of forms of commonwealths must be to make the empire of reason flourish" (Leibniz 1988: 193). It is important to understand exactly what Leibniz means by that expression. What Leibniz rejects above all in the realm of politics was the reign of arbitrary power, the subordination of wisdom to unbridled force or, what for him amounted to the same, freedom separated from reason. He did not believe in freedom in the negative Hobbesian sense of unimpeded exercise of power but understood "true liberty" in the Aristotelian sense of rational spontaneity, as "the power of following reason" (Leibniz 1988: 194). This meant, of course, that he was a constant and outspoken critic of political theories, such as Hobbes's, that did not include rationality as an intrinsic component of a political rule's legitimacy. But it also meant that he saw rationality as a higher goal than freedom.

Hence, contrary to a contemporary political philosopher like Spinoza, freedom of expression and the safeguarding of individual liberties did not figure on the top of the list of his political agenda [START_REF] Laerke | Leibniz: Moderation and Censorship[END_REF]. Instead, his political project focused mostly on the promotion of rationality and peace through wise government, just laws, ecclesiastical harmony, civic education and scientific progress. In many respects, the Republic of Letters, the scientific communities and the educational institutions, academies and universities, represented for Leibniz a kind of international super-structure in charge of promoting the empire of reason [START_REF] Roldan | Perpetual Peace, Federalism and the Republic of the Spirits: Leibniz Between Saint-Pierre and Kant[END_REF]2016).

An essential precondition, however, of such flourishing and Enlightenment was "balance in Christianity and tranquility in Europe" (A IV, ix [ve], 212). 5 For Leibniz, human societies suffered from three essential evils: plague, famine and war. But where, oddly enough, he considered the first two evils something that could be resolved within the borders of each nation, ending wars among the states of Europe would obviously require a concerted effort of "some great princes" (Leibniz 1988: 177). Leibniz, like St. Pierre, saw the urgent need for a stable peace in Europe, based on a less volatile foundation than the accumulation of fragile treatises that were constantly violated, each time throwing the region off balance (Leibniz 1988: 166-67). Hence, Leibniz constantly complained of how the French, in particular, rather than supporting equitable long-term alliances, forced neighboring states into accepting successive treatises reflecting only current power relations, invariably in their own favor, by means of "cruel violence and most iniquitous usurpations" (A VI, iv, 476). 6 In conformity with Leibniz's ideal of an empire of reason, a new balance of Europe was not only to be a balance of power, but rather a balance of reason, or a balance of justice, where the just 5 For Leibniz's explicit use of the political commonplace of a "balance of Europe," see e. g. A IV,i,211,214,A IV,iii,167;A IV,iv,344,468;A IV,ix [ve], 218. The notion figures in the title of André Robinet's book on Leibniz's political philosophy [START_REF] Robinet | Le Meilleur des mondes par la balance de l[END_REF]. Luca Basso and Peter Nitschke have also stressed the centrality of the notion [START_REF] Basso | Regeln einer effektiven Aussenpolitik -Leibniz' Bemühen um eine Balance widerstreitender Machtinteressen in Europa[END_REF][START_REF] Nitschke | Die Leibnizsche Vision von Europa[END_REF] 6 The 1672 French invasion of Holland, and subsequent Treatise of Nijmegen in 1678-79, represented for Leibniz the best example of such French "iniquitous usurpations" and of how they paid off. The 1685 Revocation of the Nantes Edict and the persecution of the Huguenots was the best example of France's "cruel violence." See also Riley 1996: 245-60. mean was to be established by adhering in good faith to the outcomes of rational deliberation rather than by opposing force to force. Such rational deliberation, or "balancing of reasons," was for Leibniz, a jurist, essentially conceived on the model of a legal reasoning in a court of law: "In order to maintain public security, the principal powers of Europe must hold on to the scales of Themis and declare themselves in favor of justice and good faith in promises and pledges" (Leibniz 1923-: IV, ix [ve], 191). 7 Hence, when St. Pierre proposed that Leibniz compose a work of his own on "European Arbitration," he really did hit the nail on the head.

The following is an attempt to reconstruct, in broad strokes, on the basis of passages gleaned from disparate texts and periods, what such a work might have looked like and what kind of political model for a European union it would have recommended.

The Imperial Model

Leibniz's vision of Europe cannot be separated from the fact that he was a staunch defender the Holy Roman Empire about which he wrote a great deal [START_REF] Nitschke | Die Leibnizsche Vision von Europa[END_REF]. This does, of course, reflect the fact that Leibniz was German and employed by an electoral Prince. Most of Leibniz's texts on imperial politics aimed at consolidating and defending the already existing federal structures among the German states. These structures did however also point to a prospective broader ideal of a politically united Europe, since, for him, the Empire was "like a model for the Christian society" (Leibniz 1988: 181). Hence, if Leibniz had a vision for Europe, it took the form of an expanded Holy Roman Empire. It would however be misguided to consider his predilection for the Empire a mere expression of political partisanship. Leibniz also had other, more theoretical reasons for linking any possible union of Europe as a whole to the already existing Empire.

First, the Empire provided a coherent federalist model of sovereignty [START_REF] Nitschke | Die Leibnizsche Vision von Europa[END_REF][START_REF] Nitschke | Die (föderale) Ordnungsvision von Leibniz für Europa[END_REF]. Leibniz was strongly opposed to Samuel Pufendorf who declared the Empire a monstrous construction on account of it being in constant violation with the principle of indivisibility of sovereignty (Pufendorf 1667;Leibniz 1988: 119). Leibniz's formulated his alternative model in two texts: the lengthy Caesarinus fürstenerius and the Entretien de Philarèthe et d'Eugène, a French summary in dialogue form, both from 1677 (A IV, ii, 3-270 7 Cf. Leibniz's Letter on the education of a Prince (1685-86), according to which "the great art of reasoning consists in knowing how to weigh reasons like in a balance, in order to favor the side that wins: one must lead the Prince to reason in morals, in politics and in law […]" (A IV, iii, 553). Generally, on Leibniz's central conception of a "balance of reason" (trutina rationis) see, among other texts, A VI, i, 548-59; A I, ii, 168; A VI, iv, 2250, 2259, etc. For a commentary, see [START_REF] Dascal | La Balanza de la razon[END_REF]. and 278-46; for English excerpts from the first, see Leibniz 1988: 111-20). According to these texts, the essence of sovereignty is not, like for Bodin, Hobbes, or Pufendorf, indivisible coercive power. Instead, it relies on two factors: internal territorial hegemony and sufficient capacity to counter an external enemy. When those conditions are in place, so is the "public liberty," i.e. the freedom to act of the Prince upon which his sovereignty depends. This, of course, is a relative rather than absolute definition of sovereigntyin a sense, it represents an approach to international law that is more that of a diplomat than that of a political philosopher. Moreover, and just as important, it does not, on this fundamental level, make any reference to right. Contrary to Pufendorf, or Thomas Hobbes before him, Leibniz's conception of sovereignty does not tie right to power by definition: "The supreme jurisdiction and the right of public liberty (of which sovereignty is an eminent species) are essentially different things, and there is neither opposition nor connection between them" (A IV, ii, 335).

On this conception, one can dissociate coercive power and legitimate jurisdiction without violating the integrity of sovereignty. A sovereign, while remaining sovereign, can freely submit himself to the jurisdiction of another, such as a federal jurisdiction: "Several territories

[…] can unite into one body, with the territorial hegemony of each preserved intact" (Leibniz 1988: 117). Hence, as Leibniz explains, a sovereign "represents the public liberty, such that he is not subject to the tutelage of the power of anyone else, but has in himself the power of war and of alliances; although he may perhaps be limited by the bond of obligation toward a superior and owe him homage, fidelity and obedience" (Leibniz 1988: 175). This separation of legitimate jurisdiction and coercive power grounds the basic distinction in the 1677 texts between the "majesty" of the Emperor and the "sovereignty" of the Princes who freely chose to submit to him: Majesty and sovereignty are entirely different things. Majesty, when it is not only understood as a badge of honor but as a faculty of right, is the supreme jurisdiction, that is to say a right to command that entails, for those who are submitted to it, the obligation to obey. But if he who has this supreme right to command does not detain immediately the absolute right to constrain and freely execute his orders, that is to say, the ordinary right to maintain an army and garrisons within the states of those who recognize him, and that, consequently, he does not divest them of the right of peace, war and alliances, the latter maintain the jus propriae potestatis, the public liberty, and sovereignty as such. Thus, regardless of the strict obligations of fidelity and obedience that our princes owe to the Emperor and that render them subjects in the eyes of the civil law, they remain free with respect to the law of nations, and maintain sovereignty. (A IV,ii, The Empire never figures in Leibniz as a super-state and his European project is not a cosmopolitan one (Naert 1964: 71). Leibniz always granted full sovereignty to the individual federated states, retaining their public liberty and territorial hegemony. The jurisdiction of the Empire could only be enforced in virtue of the coercive power that such sovereign states voluntarily lend it (Leibniz 1988: 174). And yet, "if it is a question of what is right, one cannot refuse to Caesar some authority in a great part of Europe, and a species of primacy analogous to the ecclesiastical primacy [of the Pope]" (Leibniz 1988: 112).

Second, on Leibniz's description, and in opposition to St. Pierre's European project, the existing Holy Roman Empire afforded subjects an indirect voice in federal deliberations.

Leibniz writes:

I find that M. l'Abbé de St. Pierre is right to consider the Empire as a model for Christian society; but there is this difference, that in the [society] which would conform to his project, the complaints against the sovereign would not be allowed, instead of which, in the Empire, subjects can plead against their princes, or against their magistrates. (Leibniz 1988: 181) On the imperial model, the Emperor, in addition to being the secular arm of the universal church, should also represent the concerns of subjects beyond, and even against, those of their sovereigns. Patrick Riley here aptly compares with St. Simon's later criticism of St. Pierre in his Réorganisation de la Société Européenne (1814) according to which the latter's project would "favor the abuse of power by making sovereign's more formidable to the people," by "depriving the latter of any resource against tyranny" (cit. in Leibniz 1988: 181n). We should not, however, consider it anything like a concession to democratic accountability. In fact, Leibniz rejected democracy which he found potentially irrational and arbitrary because of the unaccountability of individual voters, and thus diametrically opposed to the empire of reason.

Arbitrary power is what is directly opposed to the empire of reason. But one must realize that this arbitrary power is found not only in kings, but also in assemblies, when cabals and animosities prevail over reason, which happens in judicial tribunals as well as in public deliberations. The remedy of a plurality of votes, given either publicly or secretly, in balloting, is not sufficient to curb these abuses. Elections serve after a fashion against cabals, and make it easy to assure oneself of votes by bad means; but they have this inconveniencethat each [voter] can follow his [own] whim and his wicked designs, without the shame of being discovered, and without being obliged to present reasons for them. (Leibniz 1988: 193) Surely, Leibniz realized that one absolute sovereign would yield an unaccountable power far more consequential than could any individual voter dissimulating his wicked and whimsical voting behavior, but he had sufficient faith in European nobility and the educational and advisory structures supporting individual Princes to deem the risks of evil tyranny under absolutism smaller than those stemming from the inherent irrationality of democracy: "I would come out against absolute power, if in our times we had seen tyrants comparable to those monsters of Emperors that Rome saw in other times. But today there is no prince so bad that it would not be better to live under him than in a democracy" (Leibniz 1988: 186). When making the Emperor the mouthpiece of "subjects," what Leibniz had in mind was rather the role of the Emperor as the secular head of the community of all believers formed by all Christians and all Christian peoples, beyond their association with individual states and nations.

Finally, Leibniz considered the Empire an advantageous model for the simple reason that it already existed and had done so for a long time. A new federation was best realized on the basis of already existing structures because it provided predictability and stability: "I do not believe that it would be just or appropriate to destroy with one stroke the rights of the Roman Empire, which has lasted for so many centuries" (Leibniz 1988: 181). Always a jurist, Leibniz called for a presumption in favor of legal precedence, requiring balanced consideration of past practice when making decisions about present action and future goals.

For this reason, when St. Pierre proposed a model for a "European Union" that did not include and accommodate the already existing structure of the Empire, Leibniz immediately objected: I intervene in favor of the Empire the integrity of which it will be neither easy nor reasonable to undo, as it would occur if your project was realized, if you do not temper it a bit […]. Hence, some, like the Elector of Bavaria and some Electors and Princes of the Imperial States, whom you combine according to their situation, you turn into immediate members of the European Union as if they had nothing to do with the Emperor and the Empire […].I think, Sir (unless you have a better suggestion) that you could leave the Empire in its integrity and thus make of it a large member of your European Union, for it already constitutes a considerable preliminary union that would save you the trouble of almost a third of what would be requires to unite the European powers. (Leibniz 1995: 91) 4. Three Degrees of Justice Leibniz's political philosophy was, as has been stressed often enough, theoretically and somewhat abstractly grounded in his conception of "universal jurisprudence" and the definition of justice as "the charity of the wise" [START_REF] Grua | Jurisprudence universelle et théodicée selon Leibniz[END_REF][START_REF] Riley | Leibniz' Universal Jurisprudence. Justice as the Charity of the Wise[END_REF]. In its more practical and concrete application, however, it was built up around a three-level conception of justice according to which no one should suffer prejudice or harm, everyone should get their due, and all should live honestly (neminem laedere; suum cuique tribuere; honeste vivere).

The tripartite division of natural law into three "degrees" or "heads," inherited from Roman Law, appears as early as the 1667 Nova methodus discendae docendaque jurisprudentia, and is repeated in a number of texts, including the preface to the 1693 Codex and the famous 1702 Méditation sur la notion commune de la justice (A VI, i, 343;Leibniz 1948: 556-67, 606-21;Leibniz 1988: 56-57, 171-74;Robinet 1994: 103-24;Laerke 2008: 221-29). Those three degrees of justice are also described in terms of strict law, equity and piety, and assimilated to the distinction between commutative justice, distributive justice, and universal justice. They are hierarchically ordered.

The lowest degree, strict law, like the Law of the Talion, calls for rigorous and unmodified application of the law according to a principle of arithmetic equivalence. It stipulates that neither persons nor states should suffer harm so as not to acquire a motive for retaliation (Leibniz 1988: 172). Such strict law must however be mitigated by equity, a principled consideration of the other's point of view sometimes associated with the cardinal virtue of charity. Equity is established according to a geometrical principle of proportion and where the consideration of the particular whole, that is to say the best interest of both myself and the other, is taken into account: "It requires that, against he who has made me suffer harm, I do not instigate a murderous war, but only seek restitution; that litigators be admitted; that you do not to others, what you would not want done to you" (A VI, i, 343-44). Piety is, absolutely speaking, like equity within a universal context, or justice when taking into account not just oneself and the other, but all and everything, including the afterlife (Leibniz 1988: 173). Universal justice is divine justice. However, on account of human finitude, our access to such divine justice must pass through other channels than reason, requiring recourse to a set of divine, positive laws: "Christians have yet another common tie, the divine positive law contained in the sacred Scriptures" (Leibniz 1988: 174). Positive divine law, of which the church is the guardian, should ensure that the Christian spirit of charity and justice will prevail even when insufficient knowledge of context makes it impossible to determine absolutely the pious (or universally equitable) course of action to take (Laerke 2008: 227-29).

This tripartite structure forms the legal framework for the institution of a just Christian commonwealth, forming the foundations of natural law and divine positive law. The same natural criteria of justice, however, exactly because they are natural, are also valid among nations (Leibniz 1988: 175). For this reason, the way in which Leibniz envisioned a possible construction of Europe included exactly three basic institutions, each responsible for their "head" of justice, namely a central European deposit bank, a European council of sovereigns, and a reformed catholic, i.e. universal, Church.

The European Deposit Bank

Leibniz suggests an European deposit bank in order to establish a punitive mechanism allowing the established, positive laws of a European union to be enforced, to the extent that such a federation in itself does not have any coercive power (this power, as will be recalled, always remains in the hands of each sovereign.) Hence, Leibniz writes to Grimarest:

[T]he most powerful do not respect tribunals at all. It would be necessary that all these gentlemen contribute a caution bourgeoise or deposit in the bank of the tribunal, a king of France, for example, a hundred million écus, and a king of Great Britain in proportion, so that the sentences of the tribunal could be executed in their money, in case they proved refractory. (Leibniz 1988: 183-84) The caution bourgeoise, a kind of guarantee, provides means to enforce international law by holding sovereign powers to their voluntary promises to respect this law by means of a pecuniary threat. The principle of proportional contributions from member states assures the kind of arithmetic equality between nations that is prescribed by strict law. The deposit Bank also provides a mechanism to ascertain that the representatives of individual states in a governing federal council (that I shall return to shortly) respect the basic procedural rules of equitable deliberation, by punishing such illegitimate "arguments" as threats of violence, bribes and inappropriate lobbying through economic sanctions. Finally, the institutional integrity of the union requires that it has a financial basis to rely on that is not controlled by the individual members but by the general council itself, thus assuring some independence of this supranational structure (Leibniz 1995: 57). Indeed, this is already, as Leibniz points out, a problem in the existing Empire: "The defect of the union of the Empire is not, as M. l'Abbé de St. Pierre seems to take it, that the Emperor has too much power, but that the Emperor, as Emperor, does not have enough. For the Empire has almost no revenues which are not alienated or neglected […]" (Leibniz 1988: 182). In short, the European deposit bank should play a double role in assuring both the financial independence of the supranational institutions of the European Union and provide some punitive leverage against members who did not respect the basic legal principles of the federation.

The European Council

The second European Institution, designed to assure equity, proportionality and reciprocity in the relations between nations, would be a council of sovereigns, sometimes also described as a tribunal or a senate, comparable to the one proposed by St. Pierre. It is important to realize however, that Leibniz did not get the idea from the Abbé. In fact, something similar had been on his mind for decades. There are multiple texts where he discusses the establishment of an international tribunal or council in order to institutionalize and stabilize European peace and collaboration over and above individual treatises and alliances. Already in the 1677 Caesarinus fürstenerius, Leibniz explains how, in the past, "the universal church has often judged the causes of princes" and how "princes have appealed to the councils." And he goes on to suggest that, in the future, something like "a general senate of Christendom," designed on the model of an ecumenical council, could form an institutional framework for consolidating international relations among European nations:

[I]f the Council were perpetual, or if there existed a general Senate of Christendom established by its authority, that which is done today by treaties and, as is said, by mediations and guarantees, would be done by the interposition of the public authority, emanating from the heads of Christendom, the Pope and he Emperorby friendly agreement, it is true, but with much more solidity than that which all treaties and guarantees have today […]. (Leibniz 1988: 112) Similarly, in an undated text written prior to 1693, while commenting on Edme Pirot's unpublished treatise De l'autorité du Concile de Trent, Leibniz envisages a new council for the Empire, here giving a clearer description of how, exactly, it could be composed, and its authority shared among its members:

The pope has appropriated a part of this power since the decline of the Roman Empire.

The rest should be shared between the sovereign power or major states that compose the Christian church, in such a way, however, that the emperor maintains some advantage as the first secular head of the Church; and the ambassadors who represent their masters in the councils together form a body in which is vested the rights of the ancient emperors and their legates. (Leibniz 1858(Leibniz -1875: I, 469) : I, 469) In the preface to the Codex, while discussing the political role of ecumenical councils long before the Reformation, Leibniz again considers how those councils played a pivotal role in the constitution of "a kind of common republic of Christian nations" jointly lead by the Pope and the Emperor but "without prejudicing the rights of kings and the liberty of princes" (Leibniz 1988: 174-75).

It is in direct and explicit prolongation of those previous reflections that Leibniz, in his

Observations on the book by St. Pierre, discusses historical precedence of a European tribunal of sovereigns:

There was a time when the Popes had half-formed something rather like this, by the authority of religion and the universal Church. […] Popes passed for the spiritual heads, and the emperors or kings of the Romans for the temporal heads, as our Golden Bull say, of the universal Church or of Christian society, of which the emperors were to be the born generals. It was like a droit des gens among Latin Christians, and the jurisconsults reasoned on this basis; one sees examples of it in my Codex Iuris Gentium, and some reflections about it in my preface. (Leibniz 1988: 180) At the time of Nicolas I and Gregory VII, Leibniz argues, the Church held such sway over secular sovereigns in virtue of their spiritual office that the latter could efficiently enforce international law.8 Certainly, Leibniz admits, this system subsequently broke down as a result of the "very bad Popes" who came after. However, "if there had been popes with a great reputation for wisdom and virtue […] they would have remedied the abuses, prevented the rupture, and sustained or even advanced Christian society" (Leibniz 1988: 180). And yet, for Leibniz, this was model that could advantageously be taken up again to create a European council, tribunal or senate, with appropriate modifications designed to forestall similar abuse and deterioration. Hence, Leibniz wrote regarding the "common tribunal" proposed by St.

Pierre, that if it was up to him, he himself "would be of the opinion to establish it in Rome itself and to make the Pope its president" (Leibniz 1995: 24). Now, Leibniz, of course, was a Lutheran or, as he preferred to call it, an "evangelical" Christian, in principle adhering to the tenets of the Augsburg Confession. And when he envisaged such a Council in Rome with the Pope as its head, what he had in mind was not the current Pope, head of the Roman Catholic Church governed by the principles of the Council of Trent, but a prospective new Pope, the ideal head of a resurrected and reunified "universal church."

The Universal Church

Historical precedence, however, seems like insufficient justification for placing a possible European union so heavily under ecclesiastical control. There is however another, more substantial possible justification for this, which concerns the third head or degree of justice, piety, as it should be defined by a universal church.

Let us briefly take a step back and consider what Leibniz took the authority and domain of the universal church to be. As an irenic thinker, Leibniz did not adhere to the territorialist solution otherwise in vigor in the Holy Roman Empire since the 1555 peace of Augsburg (cujus regio, ejus religio). For him, the authority of the true church did not and should not know national borders. This did not imply that the church should be able to dictate how sovereigns should govern, or in any way imperil their supremacy. Indeed, "even ecclesiastics, indeed all men, owe sovereigns an exterior obedience, but usque ad aras [up until the alter], and for the rest, they owe them at least to suffer without reserve" (A II, i, 752).

Hence, Leibniz wrote to Burnett, "you know my opinions when it comes to what is owed to sovereigns […] the church owes passive obedience: the reign of Jesus Christ is not of this world" (Leibniz 1875-1890: III, 306-7). For Leibniz, the church did, however, hold authority over an entirely different "territory" than the external, temporal kingdom over which secular sovereigns rule, for "all men and even sovereigns owe the church interior obedience, that is to say, deference without reserve in matters of belief, as far as it is possible for them" (A II, i,

752). As Leibniz sums up his position:

There is nothing more in agreement with true politics and the felicity of humankind, even in this world and in this life, than what I have put forward regarding the inviolable and irresistible power of the sovereign over exterior goods and the interior empire that God holds over souls through the church. (A II, i, 755).

Leibniz believed in separating the temporal and spiritual kingdoms in a way that separated the universal church from the state: "One should not confound church and nation" (Leibniz 1875-1890: III, 306; for details, see Laerke, forthcoming).This did not mean, however, that he believed that religion should be separated from politics. Quite to the contrary, he believed that only if the church was separated from the interests of each individual state could it assume the essential role in the domain of international, or rather European, politics that he envisaged for it.

How is that? As we have seen, the universal church is an institution in principle unconcerned with territorial hegemony and temporal power, holding authority only over a spiritual kingdom not of this world. This, however, also implies that its head, the Pope, if not in practice, then in principle has the impartiality required to moderate between such litigating parties as are indeed concerned with territorial hegemony and temporal power. For, exactly in virtue of the exclusively spiritual nature of a Pope's legitimate concerns, when it comes to controversies among secular powers, he is "so alien to the parties' commitments that he could not appear himself as a witness," as Leibniz defines an impartial judge in another context (Leibniz 2005: 27;cf. Laerke 2015: 100-101). It is thus in its capacity as an inherently nonsecular institution that the church is ideally situated to act as judge and moderator in conflicts among secular sovereigns. This was doubtless the principal reason why Leibniz wished to revive the early medieval model where the Pope "occupied the position as judge among Christian Princes" (Leibniz 1995: 24).

The medieval model, however, deteriorated as a result of evident abuse, leading to loss of faith in the spiritual mission of the Roman Catholic Church and suspicion towards the integrity of the papacy, and eventually to religious schism. This theological disaster did, however, not only do damage to the church and to the advancement of God's spiritual kingdom. It also made it impossible for the church to fulfill its designated role as impartial judge and moderator in charge of litigating conflicts between secular rulers. With the advent of schism, the Christian commonwealth of Europe not only forfeited past religious unity. It also lost the only existing institution that could possibly preside as an impartial judge over a future political council of sovereigns. And by doing this, it also forfeited the possibility of future political unity.

The Political Scandal of Schism

For Leibniz, then, any prospect for a European Union was predicated on the healing of schism and the restoration of a catholic, i.e. universal, church. In principle, for Leibniz, this was not a futile enterprise: "[I]f five or six persons wanted to, they could end the great schism in the West, and put the Church in good order" (Leibniz 1988: 177). No doubt Leibniz counted himself among those "five or six persons." He spent a life-time in irenic negotiations. He first tried to establish the dogmatic and ecclesiastical foundations for a reunion of all the Christian confessions in his epistolary exchanges throughout the 1690s with the French Bishop Jacques-Bénigne Bossuet (Antognazza 2009: 219-221, 340-41, 405-406). Later, when that project failed for reasons that Leibniz's attributed to the French Bishop's intransigence, he instead engaged in negotiating Protestant Church reunion between the Lutheran Court of Hanover and the Calvinist Court of Berlin, in his exchanges from 1698-1706 with Gerhard Wolter Molanus, Bishop of Loccum, and Daniel Ernst Jablonski, the Berlin Court preacher, [START_REF] Leibniz | Negotium Irenicum. L'union des Églises protestantes selon[END_REF]. That project, however, also failed. It is doubtless in light of these frustrating experiences that we must assess the eventually grim assessment that Leibniz gave in his 1712 letter to Grimarest, where, after recommending the constitution of a general European council presided by the Pope and residing in Rome, he added as preliminary conditions for success a long and sobering list of major church reforms:

[…] the ecclesiastics would have to reacquire their ancient authority, so that a ban or excommunication would make Kings and Kingdoms tremble, like in the time of Nicolas I. or Gregory VII. And in order to make the Protestants agree to it, one would have to ask His Sanctity to bring the Church back to the form it had in the time of Charlemagne, when he held the Council of Frankfurt, and to renounce on all the councils held ever since, for they cannot pass as ecumenical. It would also be necessary that the popes resemble the first bishops of Rome. So there we have some projects that would succeed as easily as that of the Abbé de St. Pierre. But since it is permitted to write novels, why should we find so bad this fiction of his which brings us back the Golden Age? (Leibniz 1995: 24) At this point, throwing his hands up in recognition of the futility of even trying to achieve that much, Leibniz relegated the entire enterprise to the domain of a well-meaning fiction (Riley 1996: 243-44).

So what should we conclude from this regarding the ultimate aim of restoring "Christian balance and tranquility of Europe"? Was there, for Leibniz, any chance that "we should ever be so happy as to see the affairs of Europe restored to their right balance" (A IV, iii, 167)? As it appears, prospects were bleak, but we can also draw some conclusions from the letter about why exactly they were bleak.

To be sure, for Leibniz, the first very concrete political obstacle to any restoration of balance was Louis XIV, this "most Christian war-God" as Leibniz mockingly called him.

From the French invasion of Holland in 1672 to the Revocation of Nantes Edict in 1685, Leibniz became progressively more frustrated with how the French King's blatant disrespect for the principles of international law constantly panned out in favor of this "public enemy" (A VI, iv, 476). Yet he knew that individual rulers and their individual political programs, no matter how misguided, were not the real problem. The letter to Grimarest, listing the formal requirements for engaging in a European project, makes no mention of Louis XIV or other sovereigns, but speaks only of church reform. Kings come and go. After all, Louis XIV finally died during Leibniz's exchanges with St. Pierre, on 1 September 1715. On the long term, the more preoccupying concern for any stable European Union was the absence of a basic institutional component necessary for establishing a well-functioning council or tribunal of European arbitration, namely an appropriate judge and president. For Leibniz, the only legitimate judge of controversies among the Christian princes of Europe would be the church.

It alone could preside as judge and moderator in disputes among Christian sovereigns exactly because it did not and should not have a stake in temporal matters, its kingdom being of another world. However, absent a reunified and universally recognized reformed Roman Catholic Church, the required impartiality was neither assured nor recognized, and consequently this indispensable structural component of any possible European union remained amiss. Church unification was, for Leibniz, of intrinsic theological value. But he also pursued his irenic ambitions in view of the political role that a reunited church could eventually play within a prospective broader European union or, at least, within a strengthened Holy Roman Germanic Empire. And I would suggest that his ultimately grim assessment of the prospects for Europe directly reflected the successive failures of his irenic negotiations.

Leibniz in Europe Today

It is clear enough that it would make no good sense to promote a Leibnizian vision for Europe in any straightforward way today. Leibniz's Europe did not look like ours. From the time Leibniz entered politics in the early 1670s and for the next four decades to come, the most pressing European problem was the aggressively expansionist politics of a French Monarch, who died only one year before Leibniz, and who posed a constant threat to the fragile Holy Roman Empire, still recovering from the brutal Thirty Years War that ended only two years after Leibniz was born. Moreover, the premises of his political philosophy were different. He did not believe in the benefits of democracy because he had very little faith in the rationality of the multitude. Leibniz, like Kant after him, preferred rule by enlightened monarchs and Princes (see e.g. his Lettre sur l'éducation d'un Prince, A IV, iii, 542-57, esp. 547). His vision of politics was caught up in religious institutions in ways that would be unacceptable today. He did not favor freedom of expression or tolerance in a way comparable to modern, liberal conceptions. And if he worked relentlessly toward securing peace within Europe, when it came to broader international relations, he could hardly pass for being a peace-keeper, especially with regard to the Muslim world (he did all he could to make Louis XIV invade Egypt and constantly encouraged the Emperor's ongoing war against the Ottoman Empire.)

It is of course possible to put to one side those issues and focus on the virtues of the abstract philosophical conceptions of natural law, universal jurisprudence and divine government that underlie many of his reflections on European politics [START_REF] Riley | Leibniz' Universal Jurisprudence. Justice as the Charity of the Wise[END_REF][START_REF] Roldan | Perpetual Peace, Federalism and the Republic of the Spirits: Leibniz Between Saint-Pierre and Kant[END_REF]. And yet, I think there is more to learn from Leibniz's conception of Europe if we focus on less high-flying ideals than universal benevolence, world harmony and divine justice.

Leibniz does, of course, support all of these ideals. But his political philosophy, including his conception of international law and Europe, certainly does not reduce to them and cannot be adequately explained in terms of them alone. Moreover, it is not clear to me of what concrete use those ideals could possibly be today. By the end of his life, even Leibniz himself had little confidence they could ever be realized in Europe. To my mind, there is more to learn from the strategies and arguments Leibniz malgré tout deployed to advance them, and this in many ways in spite of (rather than in virtue of) the theologically grounded universalist ideals they served to support. Some arguments have considerable provocative value by being both obviously strong and yet perfectly at odds with deeply entrenched ideals of liberal democracy. This is the case, strikingly, with the things Leibniz has to say about the inherent irrationality of democratic elections in a premonitory passage that bears repeating: "Elections serve after a fashion against cabals, and make it easy to assure oneself of votes by bad means; but they have this inconveniencethat each [voter] can follow [own] whim and his wicked designs, without the shame of being discovered, and without being obliged to present reasons for them" (op. cit.). This is also the case with his argument stressing the importance of a nonsecular institution to arbitrate among secular states. Absent a universally recognized spiritual authority, what institution today could possibly bear the stamp of impartiality required to be recognized by all as an impartial judge and moderator in deliberations among European nations? Other arguments, mutatis mutandi, have pretty straightforward application to current state of affairs. This is true, I think, for his admonitions against European politics based on individual treatises and current power relations rather than on stable, rationally negotiated, well-balanced alliances. The same goes, in some measure, for his non-absolutist notion of sovereignty from which nationalist politicians pushing misguided agendas of "taking back control from Europe" could learn a great deal.

On commerce, note a memorable quip in the Considérations sur les interests de Bronsvic (c.1691), A IV, iv, 344: "Businessman have little concern for the balance of the affairs of Europe as long as the income exceeds the expenses on the balance of their accounting."

The volumes A IV, i-vii and ix [ve], covering the period 1667 to 1701, are currently (2017) available. Other, later material, can be found in older editions, e.g.Leibniz 1858-1875[START_REF] Leibniz | Mittheilungen aux Leibnizens ungedruchten Schriften[END_REF]

 is considered the first to vindicate pontifical power over the imperial power, proclaiming the Pope the divinely ordained judge and director of sovereigns and emperors. As for Gregory VII (1073-1085), Leibniz mainly has in mind the so-called Investiture Controversy with the German Emperor Henry IV.