explanation an act of making something intelligible or understandable, as when we explain an event by showing why or how it occurred. Just about anything can be the object of explanation: a concept, a rule, the meaning of a word, the point of a chess move, the structure of a novel. However, there are two sorts of things whose explanation has been intensively discussed in philosophy: events and human actions.
Individual events, say the collapse of a bridge, are usually explained by specifying their cause: the bridge collapsed because of the pressure of the flood water and its weakened structure. This is an example of causal explanation. There usually are indefinitely many causal factors responsible for the occurrence of an event, and the choice of a particular factor as ‘the cause’ appears to depend primarily on contextual considerations. Thus, one explanation of an automobile accident may cite the icy road condition; another the inexperienced driver; and still another the defective brakes. Context may determine which of these and other possible explanations is the appropriate one. These explanations of why an event occurred are sometimes contrasted with explanations of how an event occurred. A ‘how’ explanation of an event consists in an informative description of the process that has led to the occurrence of the event, and such descriptions are likely to involve descriptions of causal processes. The covering law model is an influential attempt to represent the general form of such explanations: an explanation of an event consists in ‘subsuming,’ or ‘covering,’ it under a law. When the covering law is deterministic, the explanation is thought to take the form of a deductive argument: a statement – the explanandum – describing the event to be explained is logically derived from the explanans – the law together with statements of antecedent conditions. Thus, we might explain why a given rod expanded by offering this argument: ‘All metals expand when heated; this rod is metallic and it was heated; therefore, it expanded’. Such an explanation is called a deductive-nomological explanation. On the other hand, probabilistic or statistical laws are thought to yield statistical explanations of individual events. Thus, the explanation of the contraction of a contagious disease on the basis of exposure to a patient with the disease may take the form of a statistical explanation. Details of the statistical model have been a matter of much controversy. It is sometimes claimed that although explanations, whether in ordinary life or in the sciences, seldom conform fully to the covering law model, the model nevertheless represents an ideal that all explanations must strive to attain. The covering law model, though influential, is not universally accepted. Human actions are often explained by being ‘rationalized’ – i.e., by citing the agent’s beliefs and desires (and other ‘intentional’ mental states such as emotions, hopes, and expectations) that constitute a reason for doing what was done. You opened the window because you wanted some fresh air and believed that by opening the window you could secure this result. It has been a controversial issue whether such rationalizing explanations are causal; i.e., whether they invoke beliefs and desires as a cause of the action. Another issue is whether these ‘rationalizing’ explanations must conform to the covering law model, and if so, what laws might underwrite such explanations. See also CAUSATION, COVERING LAW MODEL , PHILOSOPHY OF SCIENC. J.K.