Colin Pittendrigh was a biologist who founded the field of chronobiology, the study of biological clocks - circadian rhythms. He showed that they are independent of any of the biological processes that use them and independent of the physical environment such as diurnal or monthly cycles, though correlated with them.

Pittendrigh's great contribution to the philosophy of biology was the first use of the term "teleonomy" to distinguish the appearance of purpose in biological evolution, specifically Darwinian natural selection, from the ancient idea of "teleology," Aristotle's "telos" or "final cause," a cosmic purpose pre-existing the appearance of life.

Today the concept of adaptation is beginning to enjoy an improved respectability for several reasons: it is seen as less than perfect; natural selection is better understood; and the engineer-physicist in building end-seeking automata has sanctified the use of teleological jargon. It seems unfortunate that the term 'teleology' should be resurrected and, as I think, abused in this way. The biologists' long-standing confusion would be more fully removed is all end-directed systems were described by some other term, like 'teleonomic', in order to emphasize that the recognition and description of end-directedness does not carry a commitment to Aristotelian teleology as an efficient [sic] casual principle.

Adaptation, Natural Selection, and Behavior, in Anne Roe and George Gaylord Simpson (eds.), Behavior and Evolution (New Haven, 1958), 390-416.,

Jacques Monod made use of the term teleonomy in his great 1971 work, Chance and Necessity. without mentioning Pittendrigh.

Ernst Mayr provided the Pittendrigh reference in a 1974 article in Boston Studies in the Philosophy of Science. But Mayr thought the uses of "teleology" needed clearer definitions.

The teleological dilemma, then consists in the fact that numerous and seemingly weighty objections against the use of teleological language have been raised by various critics, and yet biologists have insisted that they would lose a great deal, methodologically and heuristically, if they were prevent from using such language. It is my endeavor to resolve this dilemma by a new analysis, and particularly by a new classification of the various phenomena that have been traditionally designated as 'teleological'.

Teleological and Teleonomic: A New Analysis, Boston Studies in the Philosophy of Science, Volume XIV, pages 91 -117.

Mayr argued that as early as 1943 Norbert Wiener and his colleagues had shown how communications and control systems utilizing negative feedback can explain goal-directed behavior.

We owe a great debt of gratitude to Rosenblueth et al. (1943) for their endeavor to find a new solution for the explanation of teleological phenomena in organisms. They correctly identified two aspects of such phenomena, (1) that they are seemingly purposeful being directed toward a goal, and (2) that they consist of active behavior. The background of these authors was in the newly developing field of cybernetics and it is only natural that they should have stressed the fact that goal directed behavior is characterized by mechanisms which correct errors committed during the goal-seeking. They considered the negative feedback loops of such behavior as its most characteristic aspect and stated "teleological behavior thus becomes synonymous with behavior controlled by negative feedback." This statement emphasizes important aspects of teleological behavior, yet it misses the crucial point: The truly characteristic aspect of goal-seeking behavior is not that mechanisms exist which improve the precision with which a goal is reached, but rather that mechanisms exist which initiate, i.e. 'cause' this goal-seeking behavior. It is not the thermostat that determines the temperature of a house, but the person who sets the thermostat. It is not the torpedo which determines toward what ship it will be shot and at what time, but the naval officer who releases the torpedo. Negative feedbacks only improve the precision of goal-seeking, but do not determine it. Feedback devices are only executive mechanisms that operate during the translation of a program.

Teleological and Teleonomic: A New Analysis, Boston Studies in the Philosophy of Science, Volume XIV, p. 98.

Mayr wrote to Pittendrigh to explore his intentions in creating the term "teleonomy."

Pittendrigh replied,

You ask about the word 'teleonomy'. You are correct that I did introduce the term into biology and, moreover, I invented it. In the course of thinking about that paper which I wrote for the Simpson and Roe book (in which the term is introduced) I was haunted by that famous old quip of Haldane's to the effect that 'Teleology is like a mistress to a biologist: he cannot live without her but he's unwilling to be seen with her in public'. The more I thought about that, it occurred to me that the whole thing was nonsense - that what it was the biologist couldn't live with was not the illegitimacy of the relationship, but the relationship itself. Teleology in the Aristotelian form has, of course, the end as immediate, 'efficient' cause. And that is precisely what the biologist (with the whole history of science since 1500 behind him) cannot accept: it is unacceptable in a world that is always mechanistic (and of course in this I include probabilistic as well as strictly deterministic). What it was the biologist could not escape was the plain fact – or rather the fundamental fact – which he must (as scientist) explain: that the objects of biological analysis are organizations (he calls them organisms) and, as such, are end-directed. Organization is more that mere order; order lacks end-directedness; organization is end-directed. [I recall a wonderful conversation with John von Neumann in which we explored the difference between 'mere order' and 'organization' and his insistence (I already believed it) that the concept of organization (as contextually defined in its everyday use) always involved 'purpose' or end-directedness.

I wanted a word that would allow me (all of us biologists) to describe, stress or simply to allude to – without offense – this end-directedness of a perfectly respectable mechanistic system. Teleology would not do, carrying with it that implication that the end is causally effective in the current operation of the machine. Teleonomic, it is hoped, escapes that plain falsity which is anyhow unnecessary. Haldane was, in this sense wrong (surely a rare event): we can live without teleology.

The crux of the problem lies of course in unconfounding the mechanism of evolutionary change and the physiological mechanism of the organism abstracted from the evolutionary time scale. The most general of all biological 'ends', or 'purposes' is of course perpetuation by reproduction. That end [and all its subsidiary 'ends' of feeding, defense and survival generally] is in some sense effective in causing natural selection; in causing evolutionary change; but not in causing itself. In brief, we have failed in the past to unconfound causation in the historical origins of a system and causation in the contemporary working of the system…

You ask in your letter whether or not one of the 'information' people didn't introduce it. They did not, unless you wish to call me an information bloke. It is, however, true that my own thinking about the whole thing was very significantly affected by a paper which was published by Wiener and Bigelow with the intriguing title 'Purposeful machines'. This pointed out that in the then newly-emerging computer period it was possible to design and build machines that had ends or purposes without implying that the purposes were the cause of the immediate operation of the machine.

Teleological and Teleonomic: A New Analysis, Boston Studies in the Philosophy of Science, Volume XIV, pages 91 -117.

In his Metaphysics, Aristotle himself introduced the idea of an entity that has developed an internal purpose. He called it "entelechy," which has confused many modern thinkers. But is is very close to the idea of teleonomy.

Aristotle combined three Greek words - εν (in), τελος, and εχειν (to have), so εντελεχεια has the meaning of "having the telos/purpose within." This is what Pittendrigh and many later biologists see going on in all living things, clearly their "'ends' of feeding, defense, and survival generally."

Terrence Deacon defines teleonomic as "teleological in name only" (Deacon prefers "teleodynamic," see his Glossary), which is odd considering the historical purpose of the term in biology, i.e., that goal-directed purposes in biological systems require no teleological final causes pre-existing life.