Teleology

Teleology (from τέλος, telos, 'end', 'aim', or 'goal', and λόγος, logos, 'explanation' or 'reason') or finality is a branch of causality giving the reason or an explanation for something as a function of its end, its purpose, or its goal, as opposed to as a function of its cause.

A purpose that is imposed by human use, such as the purpose of a fork to hold food, is called extrinsic. Natural teleology, common in classical philosophy, though controversial today, contends that natural entities also have intrinsic purposes, regardless of human use or opinion. For instance, Aristotle claimed that an acorn's intrinsic telos is to become a fully grown oak tree. Though ancient atomists rejected the notion of natural teleology, teleological accounts of non-personal or non-human nature were explored and often endorsed in ancient and medieval philosophies, but fell into disfavor during the modern era (1600–1900).