Teleology (τέλος, an end, and λόγος, discourse) is the doctrine or general philosophical discussion of the subject of causes. It may be ultimate, reaching to God, or proximate, contemplating the more immediate purpose. The word teleology is applied to the argument from design in proof of the Deity. Also, when a natural philosopher assigns the purpose or end of any natural arrangement, as the offensive or defensive weapons of an animal, he is said to give a teleological explanation. "Existences must be considered as standing in relation, not merely to causae efficientes (to their immediate causes), but also to causae finales; indeed, the cause efficientes themselves must be conceived as moved by the cause finales, or, in other words, by the eternal rational ends meant to be subserved by created objects, which ends, although in one respect yet awaiting realization in the future, must in another respect be supposed to be already operative. We cannot fully understand realities unless we look forward to the results intended finally to be attained. Present actualities thus acquire a double significance and receive a double explanation. The whole of modern speculation has a teleological character" (Martensen, Christ. Dogmat. p. 78 sq.).