Edward Feser, Aristotle’s Revenge: The Metaphysical Foundations of Physical and Biological Science (Neunkirchen-Seelscheid: Editiones Scholasticae, 2019), 36-38.

Final causality is also known as “teleology” (from the Greek telos or “end’), a term which in contemporary usage has several misleading connotations. For example, it is often assumed that to attribute teleology to something is ipso facto to think of it as a kind of artifact which has been “designed.” That is not the case. Consider once again the examples of the liana vine and the hammock Tarzan makes out of liana vines. A hammock has a specific teleology, namely to function as a bed, and of course it is indeed an artifact which was designed by human beings to serve this function. But a liana vine also has a certain teleology insofar as it tends toward activities like taking in water and nutrients through its roots, growing in a specific way, and so on. Yet a liana vine is not an artifact but a natural substance. The reason it tends toward the activities it does is not because some human designer makes it do so (as Tarzan makes the liana vines serve the function of a hammock) but rather because that is simply what liana vines by nature do as long as nothing impedes them from doing it. Something that didn’t do so just wouldn’t be a liana vine.

In other words, liana vines and other natural substances have their teleological properties in an intrinsic or built in way, whereas artifacts like hammocks have their teleological properties in an extrinsic or externally imposed way. This reflects the fact that liana vines and other natural objects have substantial forms, whereas hammocks and other artifacts have only accidental forms. The liana vines that make up Tarzan’s hammock have no tendency on their own to function as a bed. That end or final cause has, like the form of a hammock itself, to be imposed on them from the outside. By contrast, the vines do have a tendency on their own to take in nutrients, exhibit certain growth patterns, etc. That tendency, like the form of being a vine itself, is built into them.

So, from an Aristotelian-Thomistic point of view, to be a natural substance is precisely not to be an artifact, because to be an artifact is to have a merely accidental form and extrinsic teleology, whereas to be a natural substance is to have a substantial form and intrinsic teleology. Accordingly, if “design” involves the imposition on something of an accidental form and extrinsic teleology – after the fashion of a human artificer – then natural substances are precisely not the sorts of things that are “designed.” Now, that does not mean that they are not designed if what we mean by “design” is merely that the divine intellect is the ultimate cause of their existing and having the natures, including the natural teleological features, that they have. On the contrary, the Fifth Way of proving God’s existence put forward by Aquinas and developed by later Thomists argues precisely that even intrinsic teleology must have the divine intellect as its ultimate source. (Cf. Feser 2013b) But the Thomist nevertheless insists that the proximate source of a natural object’s teleological features is its substantial form.

The need for a divine cause simply does not follow straightaway from the existence of teleology, then, but requires further argumentation. And that argumentation takes us beyond the philosophy of nature to the branch of metaphysics known as natural theology. For the specific purposes of the philosophy of nature, a thing’s teleological features can be taken as simply a consequence of its having the substantial form it has, just as its efficient causal powers can be seen as a consequence of its substantial form. Just as we can determine what causal powers a natural substance like water, copper, or stone has by simply examining the substance itself without wondering what the divine First Cause intended in creating it, so too can we determine a natural substance’s teleological features by simply examining the substance itself, without having to wonder what the divine Supreme Intelligence had in mind. That is why you can know that copper conducts electricity, that flowing water has the power to erode stone, etc. whether or not you believe in a divine First Cause, Similarly, you can know that an acorn is inherently “directed toward” becoming an oak, that eyes are inherently “directed toward” the function of allowing us to see, etc. whether or not you believe in a divine Supreme Intelligence.

The Aristotelian-Thomistic conception of teleology is therefore very different from that reflected in “design arguments” of the kind associated with William Paley and contemporary “Intelligent Design” theory. Such arguments tend to assimilate natural substances to artifacts, and also tend thereby to reduce all teleology to extrinsic teleology and all form to accidental form They are in that respect simply incompatible with an Aristotelian philosophy of nature. Both “design argument” proponents and their atheistic critics tend to assume that to admit that there is real teleology in nature is ipso facto to commit oneself to an artificer who put it there. From the Aristotelian point of view, this is too quick and reflects too crude an understanding of teleology, for not all teleology is of the extrinsic or artifact-like kind that by definition entails a mind that put it there. The teleology found in nature is instead of the intrinsic kind. While that kind of teleology might also ultimately require a divine cause – and again, the Thomist agrees that it does – that conclusion does not follow merely from the existence of teleology itself but requires further metaphysical premises. Accordingly, the question whether teleology exists in nature can, for the purposes of the philosophy of nature, be bracketed off from the dispute between atheism and theism.

As these last remarks indicate, for the Aristotelian the existence of teleology does not by itself entail conscious awareness of the end toward which a thing is “directed.” Acorns are “directed toward” becoming oaks and the phosphorus in the head of a match is “directed toward” the generation of flame and heat, but that is not because acorns consciously desire to become oaks or because phosphorus consciously desires to generate flame and heat. There is, of course, no conscious awareness here at all. Only in human beings and other animals is there such awareness. In the vast majority of cases in which teleology exists in nature, things are “directed” or “point” toward the ends they do in an entirely unconscious and unthinking way.

As my examples also indicate – and once again contrary to Paley and “Intelligent Design” theory – for the Aristotelian the question of whether teleology exists in nature has nothing especially to do with biology. The functions of biological organs are one kind of teleology, but by no means the only kind or the most prevalent kind. For one thing, most teleology in nature is not biological. For another, most of it does not involve anything like biological function in the sense of a part’s serving to advance the good of a whole. Again, the phosphorus in the head of a match inherently “points to” or is “directed at” the generation of flame and heat. But phosphorus is inorganic, and to affirm its teleological features does not require us to see it as relating to the rest of the universe in anything like the way an eye, heart, or kidney relates to the organism of which it is a part.

Intrinsic teleology exists at at least five levels in the natural world. First, there is what the contemporary philosopher Paul Hoffman (2009) has called the “stripped-down core notion” of teleology, which is simply the bare pointing of an efficient cause towards its characteristic effect or range of effects. This is present even in the simplest inorganic phenomena. Second, there is the teleology manifest in complex inorganic processes such as the water cycle and the rock cycle, in which there are several successive stages to the causal process rather than the mere “pointing” of a cause toward a single immediate effect (Oderberg 2008). Third, there is the rudimentary sort of organic but still unconscious teleology exhibited by vegetative life. Fourth, there is the conscious organic teleology exhibited by animal-life. And fifth, there is the organic, conscious, and rational teleology exhibited in human thought and action.

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Return to Lesson 10: Teleology in Science