aitia (Greek), cause. Originally referring to responsibility for a crime, this Greek term came to be used by philosophers to signify causality in a somewhat broader sense than the English ’cause’ – the traditional rendering of aitia – can convey. An aitia is any answer to a why-question. According to Aristotle, how such questions ought to be answered is a philosophical issue addressed differently by different philosophers. He himself distinguishes four types of answers, and thus four aitiai, by distinguishing different types of questions: (1) Why is the statue heavy? Because it is made of bronze (material aitia). (2) Why did Persians invade Athens? Because the Athenians had raided their territory (moving or efficient aitia). (3) Why are the angles of a triangle equal to two right angles? Because of the triangle’s nature (formal aitia). (4) Why did someone walk after dinner? Because (or for the sake) of his health (final aitia). Only the second of these would typically be called a cause in English. Though some render aitia as ‘explanatory principle’ or ‘reason’, these expressions inaptly suggest a merely mental existence; instead, an aitia is a thing or aspect of a thing. See also ARIS- TOTLE , EXPLANATIO. E.C.H.