The natural world gives an almost irresistable semblance of teleology, or adaptedness to goals. But is this an anthropomorphic mode of thought, a subjective point of view under which we comprehend certain definite phenomena? 

In the Timaeus, Plato pictured the natural world as the product of a divine craftsman who looked to the world of eternal being for his model of the good and then created a natural order that was as good as it possibly could be. ("Teleology", by James C. Lennox, in Keller and Lloyd, eds. Keywords in Evolutionary Biology ) This model is the origin of what is sometimes referred to as "external teleology." The "externality" is twofold: the agent whose goal is being acheived is external to the object, and the value is the agent's value, not the object's. (This is much closer to the idea of the machine

Aristotle, on the other hand, is often identified as the origin of an " immanent," or "internal" teleology. Aristotle's notion differs from Plato's on both counts. The goal belongs to the organism rather than to an "external" designer, and the end to which a natural process is directed is simply the being, the life of the natural object in question. It is not a "purpose," neither man's nor God's. The kinds of "ends" that usually interest Aristotle are the determinate end-points of particular processes within the natural world. The concept of telos in Aristotle's sense applies to precisely where he invoked it: in the study of ontogenesis. 

For Kant, there could be no question of banishing the idea of purpose from biology, since the prime feature of the biological problem would be thereby overlooked -- the structure of those empirical objects that are called living organisms. Kant identified purposiveness as "the conformity to law of the contingent as such." To call an object purposive is to view the phenomenon "as if a concept had guided its production." These concepts teach us how to "spell out phenomena in order that we may be able to read them as experiences." The concept of purpose is not an independent principle for the explanation of nature, but it serves to take cognizance of nature. Observation itself depends on the teleological principle that nothing about organized products of nature is gratuitous, that there is some principle of the unity of what is diverse, even though we do not know this principle. Thus, "The harmony of nature with our cognitive power is presupposed a priori by judgment, as an aid in its reflection on nature in terms of empirical laws." (Intro, Sect V) Biologists necessarily presuppose orderly development towards a normal end. Such considerations place teleological (or teleonomic) thinking in the position of a regulative idea in Kant's sense -- a pure as if. (See Kant Critique of Judgement

In his History of Vitalism, Hans Driesch calls teleology a "descriptive concept," covering purposive processes that contribute towards an end. For Driesch, telology can also be applied to practical artefacts, such as machines, which are the result of purposive actions of men. (which for him, are unlike works of art) Driesch distinguishes between a "static" teleology which leads to "tectonic" or mechanistic theories of life as a particular combination of processes, (including evolution -- meaning preformism) and a "dynamic" teleology which describes the autonomy of vital processes and leads to vitalism."

Ludwig von Bertalanffy describes vitalism as erring in hypostasizing the concepts necessary for the teleological description of vital processes into active natural factors or entelechies. For Bertalanffy, the "organismic" point of view does not require such transcendent concepts, but studies the forces immanent in the system. "Most, if not all, life processes show themselves to be so ordered as to be directed towards the maintenance and restitution of the whole of the organism...There can be no doubt whatsoever concerning the fact that the phenomena in the organisms are largely "holistic" and "system-maintaining" and that it is the task of biology to establish the fact that, and the extent to which, this is the case. Following old modes of thought, some called this orderliness of life "purposiveness" and sought for the "purpose" of an organ or function. However, in the concept of a "purpose" a desiring or intending of the goal always appeared to be involved -- the type of idea to which the natural scientist is justly unsympathetic. Hence the attempt was made to portray purposiveness as a merely subjective and unscientific approach. In fact, in its ill formulation as the "examination of purposiveness," the holistic approach has frequently been abused: first in Darwinism, which often set up numerous, totally untenable hypotheses concerning "purposiveness" in its efforts to discover the utility value and selection value for every organ; and secondly in vitalism, which saw it as proof of the excercise of its vital factors." (From Theoretical Biology, quoted in Ernst Cassirer, The Problem of Form and the Problem of Cause, in The Logic of the Cultural Sciences, p. 94) 

Driesch's concept of the "whole" is the typical end-result which was only to be reached in the future, while the concept of the "whole" empolyed by Spemann, for example, is the momentary total state of the living system, not requiring the action of a non-material entelechy. 

The field theory of modern organismic theories becomes the site of negotiation between actual states and potential ones. 

In The Idea of Nature, George Collingwood listed as a characteristic of the modern as distinct from the Renaissance concept of nature, the reintroduction of teleology. Renaissance thinkers, he said, saw nature as a machine; final causes belonged outside it, in its origin or in its use, not within it. Modern thinkers, on the other hand, he believed were beginning to lean on a new analogy, not between nature and machines, but between nature and historical process. (Marjorie Grene, "Biology and Teleology") "The historical conception of scientifically knowable change or process was applied, under the name of evolution, to the natural world." According to Collingwood, this entailed some sort of return to Aristotle's recognition of goals in nature. Discussing Aristotle, he writes, "It is widely recognized that a process of becoming is conceivable only in that which is yet unrealized is affecting the process as a goal towards which it is directed.." "Teleological laws are a special case of causal laws, containing in the antecedent an allusion to the consequence of the explanandum." 

Darwin was happy to be credited with bringing back teleology to natural Science, to have wedded morphology to teleology. Darwinism is indissolubly bound up with the purposive idea. Darwin's concepts of "fitness," "selection," "struggle for existence," and "survival of the fittest" all have a plainly purposive character, and they exhibit a theoretical organization quite different from that of the concepts of the mathematical sciences. In the evolutionary context, certain character traits are favored because they have advantageous consequences. Selection may look like it is adapting each organism to its needs in the present, but really it is just favoring the descendants of of organisms that were adapted to their own needs in the past. Natural selection provides design without the need for an intelligent designer. (The "argument from design" provided a teleological explanation for an event that was otherwise improbable.) Nonetheless, the current "neodarwinian synthesis" postulates that there is no inherent direction or teleology to evolution, and that all teleology in nature is an illusion. For the neodarwinists, tautology replaces teleology: it should not be surprising that organisms that have actually survived are " adapted" to survival. If they weren't, they wouldn't be here. 

The cybernetic concept of teleology, developed in an article by Norbert Wiener, Julian Bigelow, and Arturo Rosenblueth, entitled "Behavior, Purpose, and Teleology," (Philosophy of Science 10: 18-24, 1943) defines purpose as an action directed towards a goal, and teleology as a goal achieved through a "circular causality" requiring negative feedback . In the traditional thinking since the Greeks a cause A results in an effect B. With circular causality A and B are mutually cause and effect of each other. Moreover, not only does A affect B but through B acts back on itself. A cannot do things to B without being itself effected.