According to Aristotle, there are four causes or ways things come into existence. Nothing can be accounted for, according to the Stagirite, without all four causes. Sometimes categorized in two kinds, these are the four:
A. Internal causes
1)material cause--that out of which a thing is made, the materials, the potentiality, intrinsic principle that allows a thing to be changed into something else [what can be observed in the thing itself].
2)formal cause--the form into which the materials were cast (so that they were not turned into something else), intelligible structure or act of something [the intrinsic pattern or form of the object distinguishing it from all others].
B. External causes
3)efficient cause--the process by which materials are made into something, moves or makes something, the agent that produces or move something [the object or process producing the object].
4)final cause--that for which, or that on account of which a thing came into being: the goal for which things evolve or the end of some process or activity [the final purpose]. This is the most important cause.