Feser later discusses scientism as the error of mistaking scientific abstractions for reality itself:[Modern Scholastic writers often distinguish three “degrees” of abstraction. The first degree is the sort characteristic of the philosophy of nature, which considers what is common to material phenomena as such, abstracting from individual material things but retaining in its conception the sensible aspects of matter. The second degree is the sort characteristic of mathematics, which abstracts not only the individuality of material things but also their sensible nature, focusing on what is intelligible (as opposed to sensible) in matter under the category of quantity. The third degree is the sort characteristic of metaphysics, which abstracts from even the quantitative aspects of matter and considers notions like substance, existence, etc. entirely apart from matter.]Abstractions can be very useful, and are of themselves perfectly innocent when we keep in mind that we are abstracting. The trouble comes when we start to think of abstractions as if they were concrete realities themselves -- thereby “reifying” them -- and especially when we think of the abstractions as somehow more real than the concrete realities from which they have been abstracted.
The irony is that while New Atheists and others beholden to scientism pride themselves on being “reality based,” that is precisely what they are not. Actual, concrete reality is extremely complicated. There is far more to material systems than what can be captured in the equations of physics, far more to human beings than can be captured in the categories of neuroscience or economics, and far more to religion than can be captured in the ludicrous straw men peddled by New Atheists. All of these simplifying abstractions (except the last) have their value, but when we treat them as anything more than simplifying abstractions we have left the realm of science and entered that of ideology.My purpose here is not to argue with Feser's conclusions, but to point out something about scientific abstractions that makes his case even stronger. The great revolution that occurred in the development of modern science was that abstractions were not simply read out of nature in the manner of classical philosophy, but read into nature by the actively creative mind. This is what Kant was getting at in this famous passage from the Preface to the Second Edition of the Critique of Pure Reason:
When Galileo rolled balls of a weight chosen by himself down an inclined plane, or when Torricelli made the air bear a weight that he had previously thought to be equal to that of a known column of water, or when in a later time Stahl changed metals into calx and then changed the latter back into metal by first removing something and then putting it back in again, a light dawned on all those who study nature. They comprehended that reason has insight only into what it itself produces according to its own design; that it must take the lead with principles for its judgements according to constant laws and compel nature to answer its questions, rather than letting nature guide its movements by keeping reason, as it were, in leading strings; for otherwise accidental observations, made according to no previously designed plan, can never connect up into a necessary law, which is yet what reason seeks and requires. (From the Cambridge Edition of the works of Immanuel Kant.)We don't necessarily need to agree with Kant's view that "reason has insight only into what it itself produces" to see that he was saying something deeply significant about modern science and its differences from classical modes of inquiry. The classical philosopher pondered nature and subjected it to rational analysis; this starts by abstracting form (principle) from being as the intellectual basis of analysis. Therefore the forms the philosopher considered were those derived from his experiential encounter with being. The modern scientist, by contrast, does not abstract his scientific principles from nature, but creates them a priori and imposes them on nature.
Consider the principle of inertia - "an object in motion tends to stay in motion and an object at rest tends to stay at rest." Inertia runs counter to our common experience because the objects of our common experience are generally subject to frictional forces, and so don't "tend to stay in motion" when they are in motion. Slide a beer across the bar and it comes to a stop after a few feet. So the principle of inertia is not something abstracted from experience, because we never really experience it. Instead, it is that marvelous invention of modern scientific inquiry, the theoretical construct. Galileo created the principle of inertia and used it to interrogate nature in his scientific experiments. Kant's point is that science works so well, and gives such transparent results, because there is nothing obscure about its principles; and there is nothing obscure about them because we ourselves create them.
Similar to inertia, the force, mass and acceleration of Newtonian physics were not abstracted by Newton from nature, like Aristotle abstracted rational animal from the nature of man. If they were, we might expect Aristotle to have discovered them. Nor is it an accident that force, mass and acceleration are mathematically related as force equals mass times acceleration. They are related in that equation because Newton created and defined them through the equation. Newton created his second law as a mathematical tool with which to interrogate nature, as Galileo had created inertia. This intellectual procedure - the creation of mathematically susceptible principles that form the basis of a subsequent investigation of nature - is the great breakthrough of modern science.
It's also why modern science is riven with priority claims in a way that classical philosophy was not. The idea that Plato might dedicate himself to a public campaign to prove that he was real inventor of the theory of the forms, and not Socrates or Aristotle, is laughable. Or that Thomas Aquinas might engage in a publicity battle to prove that he was the real originator of the cosmological argument rather than, say, Averroes. But the modern scientific world was subject to such acrimonious disputes from its inception, as exemplified in the long battle between Newton and Leibniz for the title of inventor of calculus. The reason, of course, is that Plato and Aquinas weren't inventing anything but explicating what was already given - nature - while Newton and other modern scientists were doing more than mere explication; they were inventing the tools that made the interrogation of nature possible. And over inventions there may be priority disputes.
Returning to Feser's point about the reification of abstractions, the situation under the understanding of scientific abstractions I've just presented is even worse for scientism than it is if scientific abstractions are considered as plain, old classical abstractions. Classical abstractions are at least derived from nature. In Aristotle's understanding, substance is a composite of form and matter, and the form analyzed in the philosopher's intellect is the same form as in the substance under analysis, since it is abstracted from substance. The mistake of "concretizing the abstract" is to mistake this abstracted form for fundamental reality rather than the substantial being from which it was abstracted. But the Aristotelian abstracted form at least has the advantage of being an aspect of fundamental reality, if not the whole of it. The situation is different with the theoretical constructs of modern science. They are creative products of the human mind and nature is interrogated in their terms; to reify them is to mistake pure products of the human imagination for reality itself.
This is not a novel point: Kant makes it in his Critique in the form of his distinction between the noumenal and the phenomenal. If we take science as the only true means of the investigation of reality (other than pure reason, which - according to Kant - can't issue in any genuine metaphysical insights), then what we learn through science is not reality itself, but only reality as it is interpreted through the theoretical constructs of science, which are themselves creative products of the human mind. To reify those theoretical constructs is literally to live in a fantasy world of your own creation.
It was obvious to Kant, and should be to us, that the mind that creates the theoretical constructs of science is both more real than those constructs and yet ultimately unknowable through them, since it necessarily transcends them. Henry Ford's Model T factory in Detroit could be constructed of many things, but one thing it couldn't be constructed of is Model T's, since the Model T's don't exist until the factory produces them. Similarly, the mind of Newton can't ultimately be composed of force, mass and acceleration (as strictly understood under Newton's Second Law) since those things are not naturally occurring elements, but the creative products of the genius of Newton. (It is important to keep in mind the distinction between the common sense meaning of terms like force, mass and acceleration, and their strictly scientific meaning as force, mass and acceleration. Commonsensically, mass means "how much stuff there is", but that isn't what it means under Newtonian science. What mass means under Newtonian science is the strict mathematical relationship of force divided by acceleration. And that meaning of mass is a creative product of the genius of Newton, not existent in the world until Newton created it.)
The early modern scientists and scientific philosophers like Galileo, Francis Bacon and Kant were quite self-conscious about what they were doing and the genuine revolution in thought modern science represented. Rather than being led around by the nose by nature like the classical philosophers, the modern scientist turns the tables and submits nature to an interrogation of his own invention, literally: Scientific constructs are constructs and nature is forced into their categories. The vindication of a scientific theory through repeatable experiments indicates the extent to which nature submits to the categories created by the scientific mind; but no level of vindication changes the fact that the substance of the scientific theory is a creative product of the mind rather than the substance of nature itself. These early modern philosophers saw science as a manifestation of the transcendent power and reality of the human mind: The classical philosopher thought the mind, though part of nature, transcended nature by knowing it. The modern scientific mind also transcends nature but in a way far more significant than that supposed by Aristotle. The modern scientific mind is not a part of nature at all because it is behind and prior to nature: Nature comes into existence only when spoken through the creative products of the scientific mind.