H. P. Grice, Deciding

DECISUM -- Deciding: decision Ethics [Greek prohairesis, decision, from pro, before in the sense of temporal and preferential priority + hairesis, choosing] In Aristotle’s ethics, the origin of action. His theory of decision is viewed as a predecessor of the modern theory of will. Choice may be based on emotion and appetite, while prohairesis is rational choice. Decision is a mental act that combines both thinking and desiring and comprises both a rational desire for some good as an end in itself and deliberation about how to achieve the end. It is an impulse following upon a judgment reached by deliberation. Action or decision can be the outcome of practical reason in deliberation. “For it is our decision to do what is good and bad, not our beliefs that make the characters we have.” Aristotle, Nicomachean Ethics -- decision procedure Logic A mechanistic procedure for determining whether an arbitrary well-formed formula is a theorem of a given formal system or theory by following a rule within a finite number of steps or a procedure to determine its semantic validity. A decision procedure determines whether a well-formed formula is true under any interpretation. A decision procedure is an algorithm. For instance, the truth-table is a decision procedure for propositional calculus. A proof that such a procedure exists for a theory provides a positive solution to the decision problem for that theory. Otherwise, there is a negative solution. A decision procedure is also a way of finding whether a concept can be applied in any given case. A concept connected with such a procedure is called definite and is regarded as meaningful. “A procedure of decision for a class of sentences is an effective procedure either, in semantics, for determining for any sentence of that class whether it is true or not . . . or, in syntax, for determining for any sentence of that class whether it is provable in a given calculus.” Carnap, Logical Foundations of Probability -- decision theory Ethics, philosophy of action, philosophy of social science, political philosophy The mathematically oriented theory of rational choice or decision making, which aims to make clear what is the best thing to do in a given situation. There are many situations in which an agent is faced with a set of alternatives that have various degrees of risk and various probabilities of possible outcomes being realized. Sometimes the agent has only limited knowledge of the consequences of possible actions. Decision theory helps an agent confronted with such a situation to decide the most rational way to act given the relevant available information. The common approaches include assigning probability to the outcomes of each possible action and then either to choose the action with the maximum expected utility or to choose the action that is least bad compared with other alternatives. Decision theory is philosophically interesting, because it is closely associated with notions such as preference, choice, and deliberation and is hence widely applicable in moral and political theory. Game theory is one part of decision theory, for while decision theory must take into account all factors involved, including natural and blind chance, game theory only involves interactions with the choices of other rational agents. “Decision theory as an empirical theory holds that there is some specification of alternative actions, outcomes, and beliefs about these and their probabilities, and preferences among these, such that the person acts so as (for example) to maximise expected utility.” Nozick, Philosophical Explanations