Formal semantics for propositional attitudes

CDD: 160 FORMAL SEMANTICS FOR PROPOSITIONAL ATTITUDES DANIEL VANDERVEKEN Université du Québec, Trois-Rivières CANADA Abstract: Contemporary logic is confined to a few paradigmatic attitudes such as belief, knowledge, desire and intention. My purpose is to present a general modeltheoretical semantics of propositional attitudes of any cognitive or volitive mode. In my view, one can recursively define the set of all psychological modes of attitudes. As Descartes anticipated, the two primitive modes are those of belief and desire. Complex modes are obtained by adding to primitive modes special cognitive and volitive ways or special propositional content or preparatory conditions. According to standard logic of attitudes (Hintikka), human agents are either perfectly rational or totally irrational. I will proceed to a finer analysis of propositional attitudes that accounts for our imperfect but minimal rationality. For that purpose I will use a non standard predicative logic according to which propositions with the same truth conditions can have different cognitive values and I will explicate subjective in addition to objective possibilities. Next I will enumerate valid laws of my general logic of propositional attitudes. At the end I will state principles according to which minimally rational agents dynamically revise attitudes of any mode. Keywords: Philosophical logic. Propositional attitudes. Psychological modes. Minimal rationality. 1. ANALYSIS OF PROPOSITIONAL ATTITUDES Let me first explain my componential analysis of psychological modes and the principles of my logic of propositional attitudes. (For more explanations see my paper Vanderveken (2008)). By nature attitudes, which are directed at objects and facts of the world, have logically related conditions of possession and of satisfaction. Whoever Manuscrito — Rev. Int. Fil., Campinas, v. 34, n. 1, p. 323-364, jan.-jun. 2011. 324 DANIEL VANDERVEKEN possesses an attitude is in principle able to determine what has to happen in the world in order that his or her attitude is satisfied. Beliefs are satisfied whenever they are true, desires whenever they are realized and intentions whenever they are executed. Propositional attitudes consist of a psychological mode M with a propositional content P. They are the simplest kinds of individual attitudes directed at facts. Many philosophers tend to reduce all propositional attitudes to sums of beliefs and desires. However, our intentions are much more than a desire to do something with a belief that we are able to do it. Of course, all cognitive attitudes (e.g. conviction, faith, confidence, knowledge, certainty, presumption, pride, arrogance, surprise, amazement, stupefaction, prevision, anticipation and expectation) are beliefs and all volitive attitudes (e.g. wish, will, intention, ambition, project, hope, aspiration, satisfaction, pleasure, enjoyment, delight, gladness, joy, elation, amusement, fear, regret, sadness, sorrow, grief, remorse, terror) are desires. But psychological modes divide into other components than the basic categories of cognition and volition. In my view, complex modes have a proper way of believing or desiring, proper conditions on their propositional content or proper preparatory conditions. We feel our beliefs and desires in a lot of ways. Many modes require a special cognitive or volitive way of believing or desiring. Thus, knowledge is a belief based on strong evidence that gives confidence and guarantees truth. Whoever has an intention feels such a strong desire that he or she is disposed to act in order to satisfy that desire. From a logical point of view, a cognitive or volitive way is a function fω̄ which restricts basic psychological categories. Like illocutionary forces, modes also have propositional content and preparatory conditions. Previsions and anticipations are directed towards the future. Intentions are desires to carry out a present or future action. From a logical point of view, a condition on the propositional content is a function fθ that associates which each agent and moment a set of propositions. Any agent of an Manuscrito — Rev. Int. Fil., Campinas, v. 34, n. 1, p. 323-364, jan.-jun. 2011. FORMAL SEMANTICS FOR PROPOSITIONAL ATTITUDES 325 attitude or of an illocution presupposes certain propositions. His or her attitude and illocution would be defective if these propositions were then false. Thus promises and intentions have the preparatory condition that the agent is then able to do the action represented by their propositional content. No agent can lie to himself. Whoever has an attitude both believes and presupposes that its preparatory conditions are fulfilled. A preparatory condition is a function fΣ associating with each agent, moment and propositional content a set of propositions that the agent would presuppose and believe if he had then an attitude with that preparatory condition and propositional content. The sets of cognitive and volitive ways, of propositional content and of preparatory conditions are Boolean algebras. They contain a neutral mode, preparatory or propositional condition and they are closed under the operations of union and intersection. On the basis of my analysis, one can formally distinguish different modes of attitudes like fear, regret and sadness which apparently reduce to the same sums of beliefs and desires. Identical psychological modes have the same components. Possession conditions of propositional attitudes are entirely determined by components of their mode. By definition, an agent a possesses a cognitive (or volitive) attitude of the form M(P) at a moment m when he or she then believes (or desires) the propositional content P , he or she feels that belief or desire that P in the cognitive or volitive way ω̄M proper to psychological mode M , the proposition P then satisfies propositional content conditions ΘM (a, m) and finally that agent then presupposes and believes all propositions determined by preparatory conditions ΣM (a, m, P ) of mode M with respect to the content P . Thus an agent intends that P at a moment when proposition P then represents a present or future action of that agent, he or she desires so much that action that he or she is committed to carrying it out and moreover that agent then presupposes and believes to be able to carry it out. An attitude strongly commits an Manuscrito — Rev. Int. Fil., Campinas, v. 34, n. 1, p. 323-364, jan.-jun. 2011. 326 DANIEL VANDERVEKEN agent to another at a moment when he or she could not then have that attitude without having the second. Thus whoever believes that it will rain tomorrow then foresees rain tomorrow. Some attitudes strongly commit the agent to another at particular moments. Whoever believes now that it will rain tomorrow foresees rain tomorrow. The day after tomorrow the same belief won’t be a prevision. It will be a belief about the past. An attitude contains another when it strongly commits any agent (...truncated)