rationality. In its primary sense rationality is a normative concept that philosophers have generally tried to characterize in such a way that, for any action, belief, or desire, if it is rational we ought to choose it. No such positive characterization has achieved anything close to universal assent because, often, several competing actions, beliefs, or desires count as rational. Equating what is rational with what is rationally required eliminates the category of what is rationally allowed. Irrationality seems to be the more fundamental normative category; for although there are conflicting substantive accounts of irrationality, all agree that to say of an action, belief, or desire that it is irrational is to claim that it should always be avoided. Rationality is also a descriptive concept that refers to those intellectual capacities, usually involving the ability to use language, that distinguish persons from plants and most other animals. There is some dispute about whether some non-human animals, e.g., dolphins and chimpanzees, are rational in this sense. Theoretical rationality applies to beliefs. An irrational belief is one that obviously conflicts with what one should know. This characterization of an irrational belief is identical with the psychiatric characterization of a delusion. It is a personrelative concept, because what obviously conflicts with what should be known by one person need not obviously conflict with what should be known by another. On this account, any belief that is not irrational counts as rational. Many positive characterizations of rational beliefs have been proposed, e.g., (1) beliefs that are either self-evident or derived from self-evident beliefs by a reliable procedure and (2) beliefs that are consistent with the overwhelming majority of one’s beliefs; but all of these positive characterizations have encountered serious objections.
Practical rationality applies to actions. For some philosophers it is identical to instrumental rationality. On this view, commonly called instrumentalism, acting rationally simply means acting in a way that is maximally efficient in achieving one’s goals. However, most philosophers realize that achieving one goal may conflict with achieving another, and therefore require that a rational action be one that best achieves one’s goals only when these goals are considered as forming a system. Others have added that all of these goals must be ones that would be chosen given complete knowledge and understanding of what it would be like to achieve these goals. On the latter account of rational action, the system of goals is chosen by all persons for themselves, and apart from consistency there is no external standpoint from which to evaluate rationally any such system. Thus, for a person with a certain system of goals it will be irrational to act morally. Another account of rational action is not at all person-relative. On this account, to act rationally is to act on universalizable principles, so that what is a reason for one person must be a reason for everyone. One point of such an account is to make it rationally required to act morally, thus making all immoral action irrational.
However, if to call an action irrational is to claim that everyone would hold that it is always to be avoided, then it is neither irrational to act immorally in order to benefit oneself or one’s friends, nor irrational to act morally even when that goes against one’s system of goals. Only a negative characterization of what is rational as what is not irrational, which makes it rationally permissible to act either morally or in accordance with one’s own system of goals, as long as these goals meet some minimal objective standard, seems likely to be adequate.
See also EPISTEMOLOGY , ETHICS, PRACTI- CAL REASONING , THEORETICAL REASO. B.Ge.