 Tele-dology or five-nality is a reason or explanation for something in function of its end, purpose, or goal. It is derived from two Greek words, telos and, goal, purpose and logos reason, explanation. The purpose that is imposed by a human use, such as that of a fork, is called extrinsic. Natural tele-dology, common in classical philosophy by controversial today, contends that natural entities also have intrinsic purposes, irrespective of human use or opinion. For instance, Aristotle claimed that anachron's intrinsic telos is to become a fully grown oak tree. Though ancient atomists rejected the notion of natural tele-dology, tele-logical 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 to 1900. In the late 18th century, Immanuel Kant used the concept of telos as a regulative principle in his critique of judgment. Tele-dology was also fundamental to the speculative philosophy of George Hegel. Modern philosophy philosophers and scientists are still discussing whether tele-logical axioms are useful or accurate in proposing modern philosophies and scientific theories. For instance, in 2012, Thomas Nagel proposed a nondarwinian account of evolution that incorporates impersonal and natural tele-logical laws to explain the existence of life, consciousness, and rationality.