Teleology

Teleology (from τέλος, telos, 'end', 'aim', or 'goal', and λόγος, logos, 'explanation' or 'reason')^[1] or finality^[2][3] 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.^[4]

A purpose that is imposed by human use, such as the purpose of a fork to hold food, is called extrinsic.^[3] Natural teleology, common in classical philosophy, though controversial today,^[5] 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.^[6] 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).