First order logic as a formal language : an investigation of categorial grammar.

Thesis. 1976. Ph.D.--Massachusetts Institute of Technology. Dept. of Philosophy.Microfiche copy available in Archives and Humanities.Bibliography: leaves 165-170.Ph.D

How to stop thinking : a massively modular response to the frame problem

We commonly turn to the metaphor of the mind as a sort of computer, yet we are incapable of programming a computer to perform even the simplest cognitive tasks that humanity is capable of, and this stark failure speaks to the centrality of the problem of framing. This 'frame problem' is one of determining relevance--of limiting thought regarding an impending action to that (and only that) which falls within the context at hand--in such a way that computationally tractable thought processing can take place. The simple fact is that we do, in fact, do this in day to day cognition, ubiquitously and quite efficiently. Yet it is not at all clear how we manage to do it without entailing a constant and nearly infinite revision of the entire epistemic background, resulting in combinatorial explosion. It is a question of how to stop thinking. This thesis endeavours to obviate the frame problem with a massively modular model of cognition based largely on the work of Peter Carruthers in his 2006 book The Architecture of the Mind. Where Carruthers' argument is vulnerable, other recent work in psycholinguistics is offered in defense and, ultimately, an account is presented explaining how we frame cognitive tasks in such as way as to adequately account for the inferential and holistic reasoning abilities we take for granted while still maintaining a materialist model that is neither strained by computational intractability, nor necessitates a central executive control mechanism, or 'ghost in the machine.

Voir, savoir, faire : une étude de cas en logique modale

Agents are entities who perceive their environment and who perform actions. For instance in role playing video games, ennemies are agents who perceive some part of the virtual world and who can attack or launch a sortilege. Another example may concern robot assistance for disabled people: the robot perceives obstacles of the world and can alert humans or help them. Here, we try to give formal tools to model knowledge reasoning about the perception of their environment and about actions based, on modal logic. First, we give combine the standard epistemic modal logic with perception constructions of the form (agent a sees agent b). We give a semantics in terms of position and orientation of the agents in the space that can be a line (Lineland) or a plane (Flatland). Concerning Lineland, we provide a complete axiomatization and an optimal procedure for model-checking and satisfiability problem. Concerning Flatland, we show that both model-checking and satisfiability problem are decidable but the exact complexities and the axiomatization remain open problems. Thus, the logics of Lineland and Flatland are completely a new approach: their syntax is epistemic but their semantics concern spatial reasoning. Secondly, we study on the logic of agency ''see-to-it-that'' STIT made up of construction of the form [J]A standing for ''the coalition of agents J sees to it that A''. Our interest is motivated: STIT is strictly more expressive that standard modal logic for agency like Coalition Logic CL or Alternating-time Temporal Logic ATL. In CL or ATL the ''de re'' and ''de dicto'' problem is quite difficult and technical whereas if we combine STIT-operators with epistemic operators, we can solve it in a natural way. However this strong expressivity has a prize: the general version of STIT is undecidable. That is why we focus on some syntactic fragments of STIT: either we restrict the allowed coalitions J in constructions [J]A or we restrict the nesting of modal STIT-operators. We provide axiomatizations and complexity results. Finally, we give flavour to epistemic modal logic by adding STIT-operators. The logic STIT is suitable to express counterfactual statements like ''agent a could have choosen an action such that A have been true''. Thus we show how to model counterfactual emotions like regret, rejoicing, disappointment and elation in this framework. We also model epistemic games by adapting the logic STIT by giving explicitely names of actions in the language. In this framework, we can model the notion of rational agents but other kind of behaviour like altruism etc., Nash equilibrium and iterated deletion of strictly dominated strategies.Dans le domaine des jeux vidéos par exemple, surtout des jeux de rôles, les personnages virtuels perçoivent un environnement, en tirent des connaissances puis effectuent des actions selon leur besoin. De même en robotique, un robot perçoit son environnement à l'aide de capteurs/caméras, établit une base de connaissances et effectuent des mouvements etc. La description des comportements de ces agents virtuels et leurs raisonnements peut s'effectuer à l'aide d'un langage logique. Dans cette thèse, on se propose de modéliser les trois aspects ''voir'', ''savoir'' et ''faire'' et leurs interactions à l'aide de la logique modale. Dans une première partie, on modélise des agents dans un espace géométrique puis on définit une relation épistémique qui tient compte des positions et du regard des agents. Dans une seconde partie, on revisite la logique des actions ''STIT'' (see-to-it-that ou ''faire en sorte que'') qui permet de faire la différence entre les principes ''de re'' et ''de dicto'', contrairement à d'autres logiques modales des actions. Dans une troisième partie, on s'intéresse à modéliser quelques aspects de la théorie des jeux dans une variante de la logique ''STIT'' ainsi que des émotions contre-factuelles comme le regret. Tout au long de cette thèse, on s'efforcera de s'intéresser aux aspects logiques comme les complétudes des axiomatisations et la complexité du problème de satisfiabilité d'une formule logique. L'intégration des trois concepts ''voir'', ''savoir'' et ''faire'' dans une et une seule logique est évoquée en conclusion et reste une question ouverte