Lately, there's been quite a bit of talk here regarding Edward Feser's Five Proofs of the Existence of God. It might therefore be interesting to also consider an earlier work of his which covers some of the same ground, The Last Superstition. (The real reason I'm writing this, though, is that I haven't read Five Proofs, but just finished Superstition.) Billed as an answer to the New Atheism, Feser's earlier book is in reality a condemnation of pretty much all things modern — where by “modern” what is meant is everything since the days of Hobbes and Descartes. Feser regards the Enlightenment and all that followed as a disaster for humanity, and actually seems to regret the fact that we no longer live in medieval times. As one example of where he's coming from, consider what he says about Kant. He doesn't find everything about the old German professor bad: “His views on sexual morality and the death penalty, for example, are totally reactionary; that is to say, they are correct” (216-7). However, Kant's insistence on the autonomy of the individual and on treating persons as ends-in-themselves (as opposed to treating them as mere means), are, he says, “gruesome fortune-cookie expressions of modern man's self-worship” (219). (As Dave Barry used to say, I swear I'm not making this up. Feser really appears to find individualism repulsive.)
The central argument of The Last Superstition is that the moderns made a fatal mistake in abandoning Aristotelianism, and in particular the kind of teleological explanations found in that philosophy. It is this, according to Feser, that led to such things as abortion rights, gay marriage, “scientism and hyper-rationalism” (whatever he means by the latter), and the totalitarian regimes of the 20th Century that murdered people by the millions (51). However, what Feser thinks of as Aristotelianism is actually Thomism. He doesn't so much defend Aristotle's views, he defends Aquinas's interpretation of them — or maybe it's actually Feser's interpretation of Aquinas's interpretation. I say this because he gets Aristotle wrong in at least one very important respect, as we'll see.
But first, a little bit about Aristotle's views and Feser's argument.
Aristotle thought that there are four different possible types of explanation for why things are the way they are. These are the “four causes” you've probably heard about — the material cause (that out of which something is made), the formal cause (the form or pattern it takes), the efficient cause (what brings it about), and the final cause (what its goal, purpose or end is). The modern view of causation is similar to efficient causation, so the other three may sound strange. However, one can understand what Aristotle was getting at by keeping in mind that his four causes were about the ways one can answer “why” questions about things. So, for instance, as an answer to the question “why do ducks have webbed feet?”, one might say “because it allows them to swim better.” That's an explanation in terms of a final cause. So far, no problem. Where Aristotle went wrong was in thinking that there were purposes of this sort in nature — in other words, that explanations of this type get to the bottom of things.
With the scientific revolution, teleological explanations came to be regarded as non-fundamental. The modern scientific worldview accounts for ducks' webbed feet, and everything else, by just explaining how they came to be. More importantly, these explanations do away with any need to postulate purpose or goals to nature. Natural selection shows how things like webbed feet (which serve the purpose of swimming), hearts (which serve the purpose of pumping blood), and so on, evolved without supposing that anything or anyone was “trying to accomplish” (in any sense of the word) those purposes. To put it another way, natural selection is blind; it doesn't have any ends in mind. It just happens — though of course what ends up happening ends up serving all sorts of purposes for the organisms involved.
It is this modern scientific worldview that Feser vehemently opposes (though that's putting it mildly). One reason he does so is that he thinks no one ever showed that final causes don't exist. Rather, early modern philosophers just decided to replace Aristotle's four causes with the modern concept of causation (by stipulation, he claims), and later their decision mistakenly came to be regarded as a discovery. Thus, there is no reason to accept the change. But that's a silly claim. What the scientific revolution did was provide a different type of explanation from the kinds used by Aristotle, one which accounted for everything that needed to be explained without postulating anything like goals or purposes to nature. And it makes no sense to postulate the existence of something that one does not need in one's explanations. That's why final causes are no longer used in science.
But Feser has another main reason for disagreeing with the modern view. Abandoning the four causes “created a number of serious philosophical problems that have never been settled to this day” (72). These include the mind-body problem, the free-will problem, the problem of induction, skepticism, the problem of grounding morality, etc., etc. However, the idea that the only possible solution to these problems is Aristotelianism (and in most cases, even the idea that it is a good solution) is obviously absurd. For example, with regards to the first, Feser argues that the rejection of Aristotelianism leaves only two basic alternatives: something like Descartes's dualism (which, using a common objection, he says is untenable because it makes the interaction between mind and body utterly mysterious) or the “immoralist and irrationalist” view of materialism (which he says inevitably leads to the rejection of the mind). But he's wrong on both counts. It's false that materialism “implicitly denies that [the mind] exists” (195). And, even though I'm no Cartesian dualist, I think the objection that it makes mind-body interaction mysterious, although a common objection, is weak. (The fact that something is mysterious, or unlike anything else we observe, does not mean it cannot be real. If Descartes's view were correct, then that would just mean that the mind and body interact in a way that's different from any other type of causal interaction we know of, a way that we do not yet understand.)
The change from teleological explanation to scientific causal explanation is the most important difference between the Aristotelian-Thomistic and the modern worldviews, so it's not surprising that Feser discusses the rejection of final causation more than the others. It is here, however, that Feser gets Aristotle wrong. This is more than a little ironic, given how he criticizes others for their lack of knowledge. He pokes fun at Dawkins and Dennett, in particular, for their ignorance of Aquinas. He also claims that many contemporary philosophers completely misunderstand Aristotle. These philosophers, he says, suppose that when Aristotle ascribed final causes to nature, he was claiming that inanimate objects have intentions and desires, as if “the moon is consciously trying to go around the sun, or... fire wants to produce heat” (70). I don't know where Feser got that impression; I've never once heard any philosopher claim anything of the sort. Maybe some put it that way metaphorically. But as far as I've seen, philosophers are well aware that Aristotle meant no such thing. Feser himself, on the other hand, misunderstands one very important aspect of Aristotle's view. And it is central to the most important argument in his book.
That argument is stated on pages 114-6: One cannot make sense out of regularities in nature, he claims, “apart from the notion of final causation, of things being directed toward an end or goal.” In other words, it's because things are “inherently directed toward” specific ends that they behave in a law-like manner. But something cannot be “directed toward an end unless that end exists in an intellect which directs the thing in question toward it.” And the intellect that does so is, of course, God.
If this sounds familiar, it may be because it's really just the fifth of Aquinas's "five ways" of demonstrating the existence of God. However, Feser applies it not only as an answer to atheists, but as a solution to the problem of induction. Without final causation, he claims, there is no explanation for why the moon goes around the earth in a predictable manner. It could just as easily do anything else (which is why Hume, who rejected Aristotle's philosophy, thought there was a problem here). Feser is therefore arguing that all natural regularities, every causal process that can be identified by science, is dependent on final causation. But that of course means that every event, or at the very least every macroscopic event, must have a final cause. And yet, that's not what Aristotle held.
You don't have to take my word for it. The entry on “Aristotle on Causality” in the Stanford Encyclopedia of Philosophy states that “Aristotle is not committed to the view that everything has all four kinds of causes. Rather, his view is that a scientific explanation requires up to four kinds of causes” (emphasis added). According to that article, Aristotle gave the example of a lunar eclipse as something lacking a final cause. Similarly, in Aristotle: A Very Short Introduction, author Jonathan Barnes quotes the ancient philosopher himself saying that there is “no reason for seeking a final cause in all cases,” and mentions the fact that Book V of Generation of Animals “is entirely devoted to... non-purposeful [that is, lacking final causation] parts” of animals (118). Now, this is a problem for Feser. For those animal parts that lack a purpose (e.g., vestigial organs) nevertheless undergo causation in a regular, law-like manner, just like everything else. Likewise for lunar eclipses.
Wherever Feser got his ideas from, then, it certainly wasn't from Aristotle. Maybe it was from Aquinas, though I'm not sure (like Dawkins and Dennett, I'm pretty ignorant about old St. Thomas). But what's worse is that Aristotle's view goes against most of what Feser claims in his book. If Aristotle didn't believe final causation applies to everything — and he clearly didn't — then on Feser's view it follows that he had no explanation for the lawful behavior of nature, since that is found even in those things lacking final causation. It also means that Feser can no longer claim Aristotelianism is the answer to all of the problems of philosophy. Finally, it means that Feser's entire argument against atheists, in spite of the detour he takes through Aristotle's philosophy, really boils down to Aquinas's fifth way. In other words, it consists of the claim that the only way to account for laws of nature is to suppose that a God is responsible for them — a claim for which Feser provides no support beyond stating that, otherwise, things would have no reason for behaving in a regular, predictable manner.