Teleonomy is the quality of apparent purposefulness and of goal-directedness of structures and functions in living organisms that derive from their evolutionary history, adaptation for reproductive success, or generally, due to the operation of a program.
The term was coined to stand in contrast with teleology, which applies to ends that are planned by an agent which can internally model/imagine various alternative futures, which enables intention, purpose and foresight. A teleonomic process, such as evolution, produces complex products without the benefit of such a guiding foresight. Evolution largely hoards hindsight, as variations unwittingly make "predictions" about structures and functions which could successfully cope with the future, and participate in an audition which culls the also-rans, leaving winners for the next generation. Information accumulates about functions and structures that are successful, exploiting feedback from the environment via the selection of fitter coalitions of structures and functions. These features also have been described by Robert Rosen as an anticipatory system which builds an internal model based on past and possible futures states. Teleonomy is related to programmatic or computational aspects of purpose. Richard Dawkins has also described the properties of "archeo-purpose" and "neo-purpose" in his talk on the "purpose of purpose."[1] In the later part of his working with a theory of social evolution and a related theory of world-history, Talcott Parsons adopted the concept of teleonomy as the fundamental organizing principle for directional processes and his theory of societal development in general. In this way, Parsons tried to find a theoretical compromise between voluntarism as a principle of action and the idea of a certain directionality in history.
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In 1958, Colin Pittendrigh applied the term to biology:
Biologists for a while were prepared to say a turtle came ashore and laid its eggs. These verbal scruples were intended as a rejection of teleology but were based on the mistaken view that the efficiency of final causes is necessarily implied by the simple description of an end-directed mechanism. … The biologists long-standing confusion would be removed if all end-directed systems were described by some other term, e.g., ‘teleonomic,’ in order to emphasize that recognition and description of end-directedness does not carry a commitment to Aristotelian teleology as an efficient causal principle.[2]
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In 1962, Grace A. de Laguna's "The Role of Teleonomy in Evolution"[3] fleshed the applicability of the term to biological history and adaptation.
In 1965 Ernst Mayr cited[4] Pittendrigh and criticized the last few words cited above for not making a “clear distinction between the two teleologies of Aristotle”; evolution involves Aristotle's material causes and formal causes rather than efficient causes. Mayr adopted Pittendrigh’s term, but supplied his own definition:
It would seem useful to rigidly restrict the term teleonomic to systems operating on the basis of a program of coded information. (p.42)
In 1966 George C. Williams approved of the term in the last chapter of his Adaptation and Natural Selection; a critique of some current evolutionary thought.[5] In 1970, Jacques Monod, in Chance and Necessity, an Essay on the Natural Philosophy of Modern Biology,[6] suggested teleonomy as a key feature that defines life:
Rather than reject this [goal-directedness] idea (as certain biologists have tried to do) it is indispensable to recognise that it is essential to the very definition of living beings. We shall maintain that the latter are distinct from all other structures or systems present in the universe through this characteristic property, which we shall call teleonomy. [..] It will be readily seen that, in this or that species situated higher or lower on the animal scale, the achievement of the fundamental teleonomic project (i.e., invariant reproduction) calls assorted, more or less elaborate and complex structures and performances into play. The fact must be stressed that concerned here are not only the activities directly bound up with reproduction itself, but all those that contribute-be it very indirectly-to the species' survival and multiplication. For example, in higher mammals the play of the young is an important element of psychic development and social integration. Therefore this activity has teleonomic value, inasmuch as it furthers the cohesion of the group, a condition for its survival and for the expansion of the species.
In 1974 Ernst Mayr illustrated[7] the difference in the statements:
"The Wood Thrush migrates in the fall in order to escape the inclemency of the weather and the food shortages of the northern climates."
"The Wood Thrush migrates in the fall and thereby escapes the inclemency of the weather and the food shortages of the northern climates."
If we replace the words ‘in order to escape’ by ‘and thereby escapes’, we leave the important question unanswered as to why the Wood Thrush migrates. The teleonomic form of the statement implies that the goal-directed migratory activity is governed by a program. By omitting this important message the second sentence is greatly impoverished as far as information content is concerned, without gaining in causal strength.
Subsequently philosophers like Ernest Nagel further analysed[8] the concept of goal-directedness in biology and by 1982, philosopher and historian of science David Hull joked[9] about the use of teleology and teleonomy by biologists:
Haldane [in the 1930s] can be found remarking, ‘Teleology is like a mistress to a biologist: he cannot live without her but he’s unwilling to be seen with her in public.’ Today the mistress has become a lawfully wedded wife. Biologists no longer feel obligated to apologize for their use of teleological language; they flaunt it. The only concession which they make to its disreputable past is to rename it ‘teleonomy’.
Although Aristotle believed the world as a whole has a purpose and is teleologically guided, his ancient closing argument could be taken as a statement about teleonomy given modern understanding of adaptation and feedback as "nature's craft":
It is absurd to suppose that purpose is not present because we do not observe an agent deliberating. Craft does not deliberate. If the ship-building craft were in the wood, it would produce the same results by nature. If, therefore, purpose is present in craft, it is present also in nature. The best illustration is a doctor doctoring himself: nature is like that. It is plain that nature is a cause, a cause that operates for a purpose.—Physics, Book II, ch.8, 199b
In teleology, Kant's positions were neglected for many years because in the minds of many scientists they were associated with vitalist views of evolution. Their gradual rehabilitation recently is evident in teleonomy which bears a number of features, such as the description of organisms, that are reminiscent of the Kantian conception of final causes as essentially recursive in nature. The gist of Kant's position is that even though we cannot know whether there are final causes in nature, we are constrained by the peculiar nature of the human understanding to view organisms teleologically. Thus the Kantian view sees teleology as a necessary principle for the study of organisms, but only as a regulative principle, and with no ontological implications.
Teleonomy is closely related to concepts of emergence, complexity theory[10] and self-organizing systems.[11] It has extended beneath biology to be applied in the context of chemistry.[12][13] Some philosophers of biology resist the term and still employ "teleology" when analyzing biological function[14] and the language used to describe it.[15] while others endorse it.[16]