This post is part of a series on Edward’s Feser’s book “Scholastic Metaphysics”.
Feser’s book opens  with an excellent attack on “scientism”, which he defines  to mean that “the methods of science are the only reliable ways to secure knowledge of anything”. I think his critique of scientism is very good, but that Feser needlessly limits himself to this extreme definition. His critique actually cuts deeper.
Feser begins by simply noting that this position is self-contradicting since it itself is not a scientific claim. This is a valid point against his extreme definition of scientism, but let’s abandon it and consider instead a milder scientism, that agrees that pure reasoning can also establish knowledge, such as in mathematics and epistemology – (mild) scientism will then be a philosophical truth, established by pure reason.
What’s important about Feser’s argument is that his arguments focus on invoking the limits of science . Feser writes,
“…scientific inquiry rests on a number of philosophical assumptions: the assumption that there is an objective world external to the minds of scientists; the assumption that this world is governed by regularities of the sort that might be captured in scientific laws; the assumption that the human intellect and perceptual apparatus can uncover and accurately describe these regularities; and so forth. Since scientific method presupposes these things, it cannot attempt to justify them without arguing in a circle. … There is also the question of how to interpret what science tells us about the world. For example, is the world fundamentally comprised of substances or events? What is it to be a “cause”? What is the nature of the universals referred to in scientific laws – concepts like quark, electron, atom, and so on? Do they exist over and above the particular things that instantiate them? Do scientific theories really give us a description of objective reality in the first place or are they just useful tools for predicting the course of experience? … science depends upon philosophy both to justify its presuppositions and to interpret its results” (p. 10-11)
He later notes further limits of science:
“the “laws of nature” in terms of which science explains phenomena cannot in principle provide an ultimate explanation of reality. …since the ultimate laws of nature presuppose the existence of the physical universe, they cannot intelligibly be appealed to as a way of explaining the existence of the universe.” (p. 18-19)
You don’t have to believe in Feser’s extreme definition of scientism in order to acknowledge these truths. Feser is indeed entirely correct. Science does depend on philosophy.
Now scientism is widely argued against, but it isn’t because its advocates adopt the extreme stance. Rather, “scientism” is in practice the position that philosophy can do less than the philosophers, artists, humanities professors and so on claim, and science can do much more than they suppose. Feser’s critique of scientism is important because it shows just how widely philosophy is required, even for advocates of scientism. Only philosophy can clarify and justify the presuppositions of science or the scientific method itself, ponder the interpretation of scientific theories, or, perhaps, provide ultimate explanations.
There is still a lot to argue about, however, regarding the balance of power between science and philosophy. Feser maintains that philosophy can provide us with the right underlying metaphysics, that “we can know a fair amount about the existence and nature of God through reason alone”, and presumably also use it to establish knowledge in other fields, such as ethics. Advocates of scientism usually maintain instead that philosophy can generally say nothing about the external world (god included), and that some fields that are supposedly “not scientific”, like ethics, actually are.
This argument cannot be decided at a glance. One needs to actually look at the arguments of the Scholastics, to see if for example they can indeed establish something about the world – and that’s what Feser’s book is all about. So it’s very fitting that Feser opens his book with this issue.
Feser doesn’t quite present the above argument against scientism, however. Instead, he errs in putting forward a series of arguments against scientism which are, ehm, not very successful.
Feser’s first major argument against scientism is that extreme scientism is false because either its advocate should accept that philosophy is great too, in which case extreme scientism is simply wrong, or else he should redefine “philosophy” to be part of “science”, which makes extreme scientism pointless. But in both options, what Feser effectively arrives at is not a denial of all forms of scientism, but rather a mild scientism: knowledge can be obtained by both evidence-based reasoning (inductive reasoning, science), and pure reasoning (logic, philosophy). To move forward, to show that mild scientism is wrong, Feser will need to show that there are yet further ways of knowledge (divine revelation, perhaps?), or that philosophy can establish a lot regarding e.g. god, or that science can establish little beyond the traditional “scientific” fields.
Unfortunately, Feser’s attack on scientism mostly tries the latter approach, by putting “limits” on science. He makes some good points, but overall most of his “limits” do not apply. Take, for example, the idea that science has to presuppose that there is an objective world, external to the mind of scientists. Why must we accept that as a presupposition? Why can’t we accept it, and judge its merit, as a theory?
Feser’s second major argument against scientism is that the qualitative properties by which we perceive the world – color, the feeling of heat, and so on – cannot be captured by science. Science attempts to reduce them to quantitative underlying properties, such as the frequencies of light waves or the temperature of molecules. But that, says Feser, is simply selection-bias. Science fails to find color because it cannot measure color, so it measures frequencies and calls it color. “It would be ludicrous”, claims Feser, “to suggest that if the description physics gives us of the world does not make reference to some feature familiar to us in ordinary experience, then it follows that the feature in question doesn’t exist.”
But why should we believe our folk concepts exist? The burden of proof is on Feser here, both because he is claiming something exists and, more importantly, because he multiplies ontological entities needlessly. We believe that the scientific model is the true underlying reason for our qualitative experiences because of evidence-based reasoning, because the scientific description accounts so well for the myriad aspects of our experiences. To believe, that on top of that something “qualitative” exists that makes no further difference – that is ludicrous. For example: to believe that on top of the existence of light rays in various frequencies (the existence of which Feser presumably accepts) there is also “color”, which exists in the light rays apart from their frequencies, simply because our unlearned folk conceptions and our perceptions see color instead of frequencies – that is ludicrous. It’s not evidence-based reasoning, nor pure reason – it’s just irrational thinking.
Now Feser further claims (p. 16) that denying that our qualitative conscious experiences really exist is incoherent because we base our science precisely on evaluating these same experiences. But we naturalists never deny the existence of said experiences, we just reduce them to things like underlying brain states. The pressure in the gas canister exists very much, even if it’s just a statistical property of the gas molecules rather than an independently existing property of the gas. So does the apple exist, and so does its red color, and so too the perception of this color in the brain – on the basis of which and similar perceptions we base our science. There is no incoherence here.
Feser’s third major argument is that laws of nature, and hence science, cannot provide ultimate explanations. I agree with that (we’ll perhaps get to deal with laws of nature in more depth later in the series, and I’ll explain why). But then Feser goes on to say,
“Nor will it do to suggest that ultimate explanation is not to be had anyway, so that science cannot be faulted for failing to provide it. For one thing, this is itself a philosophical claim rather than a scientific one. For another, the claim is false, as we will see later in this book when discussing the principle of sufficient reason.” (p. 20-21)
Well, it is a philosophical claim, but the claim is true. We will perhaps see that later in this series, when we’ll discuss the principle of sufficient reason. Until then, I’ll say only that mild scientism isn’t threatened by the idea that philosophy can find an ultimate explanation, but that in practice I don’t believe that it can.
Feser’s fourth argument against scientism is that the principal reason for adopting it, the success of science, is not convincing. Certainly, the success of science shows that it can acquire knowledge about the qualitative things it measures and tests. But “it simply doesn’t follow that there are no other aspects of the natural world”.
I’ve already noted above that the burden is on Feser – if he wants to claim there are other aspects to the natural world, he needs to show it. But more importantly – that’s not the main argument for accepting scientism, not precisely. Even putting aside arguments from pure reason, – it isn’t just that science is successful, but that it’s exhaustive. We believe that there are no other aspects of the natural world because there does not appear to be any room left for them. The physics we have seems to explain how we see, say, perfectly. Oh, our explanation of color vision is not truly complete. But it’s so full and elaborate, and coincides so well with all the other things that the same physics explains, and our experiments so lack any other effect that seems to imply that some other feature of reality is, even occasionally, influencing events here – that it is just implausible that we’re missing something so fundamental here. It appears eminently more reasonable that we’ve already accounted for what exists and how it works, and whatever we’re missing will be a result of the same physics that works so well to describe everything we have understood so far.
To see that that’s the case, consider if our scientific understand was more fragmented (as it once was). Say we knew the equations of the dynamics of water, and for how light bends in matter, and so on – but had no general theory, only a hodgepodge of partial theories that failed to cover significant phenomena. Then it would make sense that there is still lots of knowledge missing, lots of elements of reality we don’t know about and that might be affecting the myriad phenomena that we don’t understand. Even if we had many centuries of extremely successful (but piecemeal) science and technology, that conclusion would still hold. In reality, of course, we are in the opposite position – we do have general theories, which are immensely successful in explaining virtually all phenomena, so that the little we don’t understand seems far more likely to be explicable in the same terms then to suddenly require something completely different.
There are many other points Feser makes in this section (section 0) that I disagree with, but I’ll finish with just one: Hume’s Fork.
“Hume’s Fork, the thesis that “all the objects of human reason or inquiry may naturally be divided into two kinds, to wit, Relations of Ideas and Matters of Fact” … Now Hume’s Fork is notoriously self-refuting, since it is not itself either a conceptual truth (a matter of the “relations of ideas”) or empirically testable (a “matter of fact”).” (p. 26)
I would claim in contrast that Hume’s Fork is a conceptual truth. To somewhat simplify our discussion, let us consider only propositions. They can be true in the logical sense, where a proposition is true due to the meaning of the concepts as they’re spread out by logic; and they can be true in the empirical sense, where the proposition is true because it corresponds to reality. Thus, “Rain is wet” is an empirical truth if we’ve only seen rain and now experience that the way it feels corresponds to wetness, and “Rain is wet” is a conceptual truth if the concept we have of rain already contains that it’s wet. That there are these two possible senses to the Truth of a proposition is a conceptual truth.
“there are truths – namely those of logic and mathematics – that do not plausibly fit in-to either of the two categories Hume and his naturalist descendants would, in Procrustean fashion, try to git all knowledge into. Truths of logic and mathematics have a necessity that propositions of natural science lack and an objectivity that mere “conceptual analysis”… would seem unable to guarantee” (p. 26-27)
I would claim in contrast that mathematical and logical truths are analytic, or conceptual, truths. What objectivity they have, what correspondence with reality they have, is in much the same way as other concepts. “1+1=2” seems to have “force” in the real world, when it does, because our real-world model of what “1” and “+” and so on are corresponds well to the conceptual relations between these objects. And when the pointing goes awry, when the correspondence fails, then too the result will fail – push two clouds together, and you get one cloud.
Hume’s Fork basically is mild scientism. It says that you can think things through using pure reason (philosophy, logic, mathematics), or using evidence-based reason (empiricism, science); and that’s it, there are no further “ways of knowing”. Add to that the Humean position that morality is about discovering scientific facts such as the pivotal role of empathy is human legal thinking (his position in his Principles of Morals), i.e. that ethics is a scientific field; and Hume’s general skepticism of the ability of philosophy to establish anything, especially in metaphysics – and presto, you have mild scientism in its full form. Feser is, very much, fighting Hume and his naturalist descendants. And Hume is winning.
 This is technically still in the Introduction, but this is where the philosophical work of the book really begins.
 Feser is actually using a definition lifted directly from pro-scientism philosopher Alex Rosenberg, so it’s Rosenberg’s definition rather than Feser’s. But Feser chose to address this definition, and not others.