Four causes

The four causes are, in Aristotelian thought, categories of questions that explain "the why's" of something that exists or changes in nature. The four causes are the: material cause, the formal cause, the efficient cause, and the final cause. Aristotle wrote that "we do not have knowledge of a thing until we have grasped its why, that is to say, its cause." While there are cases in which classifying a "cause" is difficult, or in which "causes" might merge, Aristotle held that his four "causes" provided an analytical scheme of general applicability.

Aristotle's word aitia (αἰτία) has, in philosophical scholarly tradition, been translated as 'cause'. This peculiar, specialized, technical, usage of the word 'cause' is not that of everyday English language. Rather, the translation of Aristotle's αἰτία that is nearest to current ordinary language is "explanation."

Overview

In Physics II.3, I.7–9 and Metaphysics V.2, Aristotle holds that there are four kinds of answers to "why" questions:

Matter

The material cause of a change or movement. Aristotle defines matter as, "...the primary substratum of each thing, from which it comes to be per se, [substantially], and that persists in the result." - Physics I.9. Matter is what allows a thing to change, either accidentally, such as a change in shape, or substantially, such as the death of a living thing, or a compound returning to its elemental parts. Aristotle gives the examples of a table's matter being wood, or a statue's matter being bronze or marble.

Form

The formal cause of a change or movement.