As Aristotelians and Thomists use the term, intellect is that faculty by which we grasp abstract concepts (like the concepts man and mortal), put them together into judgments (like the judgment that all men are mortal), and reason logically from one judgment to another (as when we reason from all men are mortal and Socrates is a man to the conclusion that Socrates is mortal). It is to be distinguished from imagination, the faculty by which we form mental images (such as a visual mental image of what your mother looks like, an auditory mental image of what your favorite song sounds like, a gustatory mental image of what pizza tastes like, and so forth); and from sensation, the faculty by which we perceive the goings on in the external material world and the internal world of the body (such as a visual experience of the computer in front of you, the auditory experience of the cars passing by on the street outside your window, the awareness you have of the position of your legs, etc.).
That intellectual activity -- thought in the strictest sense of the term -- is irreducible to sensation and imagination is a thesis that unites Platonists, Aristotelians, and rationalists of either the ancient Parmenidean sort or the modern Cartesian sort. The thesis is either explicitly or implicitly denied by modern empiricists and by ancients like Democritus; as I noted in an earlier post, the various bizarre metaphysical conclusions defended by writers like Berkeley and Hume largely rest on the conflation of intellect and imagination. But the irreducibility of intellect to imagination is for all that undeniable, for several reasons.
Thinking versus imagining
Thinking versus imagining
First, the concepts that are the constituents of intellectual activity are universal while mental images and sensations are always essentially particular. Any mental image I can form of a man is always going to be of a man of a particular sort -- tall, short, fat, thin, blonde, redheaded, bald, or what have you. It will fit at most many men, but not all. But my concept man applies to every single man without exception. Or to use my stock example, any mental image I can form of a triangle will be an image of an isosceles , scalene, or equilateral triangle, of a black, blue, or green triangle, etc. But the abstract concept triangularity applies to all triangles without exception. And so forth.
Second, mental images are always to some extent vagueor indeterminate, while concepts are at least often precise and determinate. To use Descartes’ famous example, a mental image of a chiliagon (a 1,000-sided figure) cannot be clearly distinguished from a mental image of a 1,002-sided figure, or even from a mental image of a circle. But the concept of a chiliagon is clearly distinct from the concept of a 1,002-sided figure or the concept of a circle. I cannot clearly differentiate a mental image of a crowd of one million people from a mental image of a crowd of 900,000 people. But the intellect easily understands the difference between the concept of a crowd of one million people and the concept of a crowd of 900,000 people. And so on.
Third, we have many concepts that are so abstract that they do not have even the loose sort of connection with mental imagery that concepts like man, triangle, and crowd have. You cannot visualize triangularity or humannessper se, but you can at least visualize a particular triangle or a particular human being. But we also have concepts -- such as the concepts law, square root, logical consistency, collapse of the wave function, and innumerably many others -- that can strictly be associated with no mental image at all. You might form a visual or auditory image of the English word “law” when you think about law, but the concept lawobviously has no essential connection whatsoever with that word, since ancient Greeks, Chinese, and Indians had the concept without using that specific word to name it. You might form a mental image of a certain logician when you contemplate what it is for a theory to be logically consistent, or a mental image of someone observing something when you contemplate the collapse of the wave function, but there is no essential connection whatsoever between (say) the way Alonzo Church looked and the concept logical consistency or (say) what someone looks like when he’s observing a dead cat and the concept wave function collapse.
The impossibility of materialism
Now, the reason why intellectual activity cannot in principle be reduced to sensation or imagination is, as it happens, related to the reason why intellectual activity cannot in principle be reduced to, or entirely supervenient upon, or in any other way explicable in terms of material processes of any sort. For like mental images, the symbols postulated by cognitive scientists (“sentences in the head,” “maps,” or what have you), and any other possible purported material embodiments of thought, (a) necessarily lack the universality that concepts have, (b) necessarily lack the determinacy that concepts have, and (c) generally have exactly the loose and non-essential connection to the concepts they purportedly embody that the word “law” has to the concept law or a mental image of Alonzo Church has to the concept logical consistency.
There is no way the materialist is ever going to square this circle. To “explain” intellectual activity entirely in terms of material processes is inevitably at least implicitly to deny the existence of the former, or of some essential aspect of the former. For instance, if you identify thought with material processes, you are necessarily committed to denying, implicitly or explicitly, that our thoughts ever really have any determinate content. A number of materialists have seen this -- Quine, Dennett, and Bernard Williams are three examples -- and have decided to bite the bullet and accept that the content of all thought and language is inherently indeterminate. (This is, for instance, the upshot of Quine’s famous “indeterminacy of translation” and “inscrutability of reference” theses and of Dennett’s “two-bitser” example.)
But such claims are indefensible, for reasons James Ross has trenchantly spelled out. First, if you deny the determinacy of thought, there is no way you will be able to make sense of the vast body of knowledge embodied in mathematics and logic, all of which presupposes that we have determinate concepts. And there will in that case be no way you will be able to make sense of empirical science, which presupposes mathematics and logic, and in the name of which these materialists endorse their indeterminacy theses. Second, if you deny the determinacy of thought, then you are committed to denying that we ever determinately think in accordance with valid forms of inference -- modus ponens, modus tollens, etc. -- or that we ever really add, subtract, multiply, etc. You have to hold that we only seem to do so. But that entails that we never in fact reason logically or in mathematically sound ways. This not only (once again) makes science unintelligible, but it also undermines absolutely every argument anyone has ever given, including every argument for materialism. Third, even to deny that our thoughts ever have a determinate content -- for example, to deny that we ever determinately employ addition as opposed to Saul Kripke’s notion of “quaddition” -- you first have to grasp what addition is and then go on to deny that we ever do it. But that means that you must have a thought with a certain determinate content even to deny that you ever have thoughts with that specific content.
So, anyone who thinks that thought can even in principle be entirely material hasn’t thought carefully enough about the nature of thought. The materialist refutes materialism every time he so much as tries to argue for it. Or so I would argue, and have argued at length elsewhere (e.g. in chapter 7 of Philosophy of Mind, chapter 4 of Aquinas, and at greatest length in my forthcoming American Catholic Philosophical Quarterly article “Kripke, Ross, and the Immaterial Aspects of Thought”). But I’m not going to say anything more about that subject here, because it’s not relevant to the point I do want to make in this post. So, if you want to insist that intellectual activity is material, then fine, that’s another subject. The point for present purposes is that thinking in the strict sense -- grasping abstract concepts, formulating propositions, reasoning from one proposition to another -- is different from forming mental images or the like (even if it is somehow material in some other way).
Science is an essentially intellectual activity
Now everyone knows that this is true where physics and mathematics are concerned. Of course, we do find it useful to form mental images when we try to grasp the abstractions of these disciplines, at least initially. We draw geometrical figures on paper, think of points as little dots and of lines as the sort of thing you might draw with a ruler, imagine particles as little round objects moving about and of the structure of spacetime as like a rubber sheet we might twist around in different shapes. But none of this is strictly correct, and the deeper we understand the concepts involved, the more we see that these visual images are just crude approximations. That’s why physicists prefer to put things in mathematical terms. They are not trying to show off or to be difficult for the sake of difficulty. It is rather that it is precisely those aspects of nature which can be modeled mathematically that they are interested in as physicists. Hence to put their ideas in non-mathematical terms simply fails to get at the essence of what it is they are trying to describe. (The mistake some of them make is in assuming that a mathematical description exhausts nature, as opposed to capturing merely an aspect of nature. But that’s a different subject, which I have addressed here, here, and here.)
This was part of the point of Descartes’ consideration of the possibility that he might be dreaming when he thinks he’s awake, or that the world of his senses might be a hallucination put into his consciousness by an evil spirit. He was not interesting in providing fodder for college dorm room bull sessions or science-fiction screenwriters. Nor was he merely interested in raising and responding to the problem of epistemological skepticism. What he was trying to do was reinforce the idea that physics as he wanted to (re)define it -- and he was one of the fathers of modern science, as well as being the father of modern philosophy -- is something that can be understood only via the intellect, and not via the senses or the imagination. Even if physical theory must be tested via empirical observation, its content is something that is expressible only in highly abstract terms that we must grasp with the intellect rather in terms of what we can imagine or perceive. As with the concepts law and logical consistency (to cite some examples given above), any mental imagery we associate with the concepts we learn from a physics textbook are bound to be misleading and will have little or no essential connection to the realities to which the concepts correspond. That is precisely why modern physics is so hard -- it requires a degree of abstraction of which few are capable.
Philosophy and theology are also essentially intellectual activities
Now the key concepts of the great systems of metaphysics -- whether Platonic, Aristotelian, Thomistic or other Scholastic systems, or modern rationalist systems like those of Descartes and Leibniz -- are also of the sort that can be grasped only via a high degree of intellectual abstraction, with little or nothing in the way of assistance by mental imagery. Indeed these concepts are if anything of an even higher degree of abstraction than those dealt with by the physicist. For many of them concern not just material being, nor even the most abstract aspects of material being, but being as such. When the metaphysician inquires into the nature of existence, or essence, or causation, he wants to know not merely what it is for this or that material thing to exist or have a nature or have a cause, nor even merely what it would be for some particular immaterial thing to exist or to have a nature or a cause. He also wants to know what existence as such is, what causation as such is, and so forth. His enterprise requires taking the mind as far from mental imagery -- as far from what we can visualize, for example -- as it can possibly go. Thus, while metaphysics does not involve complex calculations or the like, it is in another respect even more difficult than physics insofar as it requires an even greater sustained effort of abstraction.
Hence, when it is said by the Scholastic philosopher or theologian that God is pure actuality, subsistent being itself, and absolutely simple, or that the human soul is the substantial form of a living human being, you are going to misunderstand these concepts completely if you think of them as literally having anything to do with what you can visualize in your mind’s eye. For example, if you think of an explosion (say) when you think of God qua Actus purus actualizing the world, or of a tiny marble-like object when you think of absolute simplicity, or the dotted-line outline of a body when you think of substantial form, you will be misunderstanding these concepts as badly as -- indeed, far worse than -- you would be misunderstanding molecules if you thought of them as literally being little balls held together by sticks, or of spacetime as if it were literally a kind if sheet with indentations in it. Similarly, if you think of Descartes’ notion of res cogitans on the model of “ectoplasm,” or goo of the sort you’d see in Ghostbusters only invisible and intangible, or as “bits of non-clockwork” (as Gilbert Ryle described it), then you will be taking it to be nearly the oppositeof what Descartes actually had in mind. For these are all quasi-material kinds of thing insofar as they imply extension and/or composition. And Descartes’ whole point was that a res cogitans is neither extended nor composed of parts. It is precisely the sort of thing you cannot visualize, nor model on the workings of any kind of material system whatsoever, even the most ethereal.
And this is where so many New Atheist types come to grief. (As I find I keep having to reassure the hypersensitive reader, no, I don’t mean all atheists. I mean the kind of atheist who seriously thinks a Richard Dawkins, Jerry Coyne, or Laurence Krauss deserves to be mentioned in the same breath with J. L. Mackie, J. Howard Sobel, or Quentin Smith.) Those among them who actually know something about science (and not merely how to shout “Science!”) are well aware that you are not going to understand physics properly if you take too seriously the mental images we tend to form when we hear terms like “spacetime,” “particle,” “energy,” and the like. They are well aware that physics requires us to abstract from ordinary experience, to move away from what we can visualize or otherwise imagine. The man on the street may think that whatever is real must be something you could in principle see, hear, touch, smell, or taste, but the more scientifically savvy sort of New Atheist knows that this is a vulgar prejudice, and that it is with the intellect rather than the senses that we truly understand the world.
And yet, when dealing with metaphysical or theological concepts New Atheist types suddenly become complete Philistines, feigning an inability to grasp anything but the most crude and literal physical descriptions. Hence if you claim that the human mind is immaterial, they suppose that you simply mustbe committed to the existence of a sort of magical goop that floats above the brain; and if you say that the universe has a cause they will insist that you must believe in a kind of super-Edison who draws up blueprints, gets out his tools, and sets to work. And when you object to these preposterous straw men, they will pretend that they cannot understand your language in any other way, that it is mere empty verbiage unless read in such a crassly mundane fashion. Of course, if they held physics to the same narrow, literalistic standard, they would have to dismiss wormholes, quantum foam, black holes, gravity wells, electric fields, centers of gravity, and on and on. (I’ve discussed this double standard before, here and here.)
It is no good to object that the predictive and technological successes of physics justify this double standard, for two reasons. First, the predictive and technological successes of physics are relevant only to the epistemic credentials of physics, but not to its intelligibility. In other words, that such-and-such a theory in physics has been confirmed experimentally and/or had various practical applications is relevant to showing that it is correct, but it is not necessarily relevant to interpreting the content of the theory. Physicists knew well enough what Einstein was claiming before tests like the 1919 and 1922 eclipse experiments provided evidence that he was right. Similarly, though string theory has proved notoriously difficult to test, we know well enough what the theory means; the trouble is just finding out whether it’s true. (No one would make the asinine claim that string theory simply must be committed to the existence of literal microscopic shoelaces unless and until some experimental test of the theory is devised.)
So, even if it were correct to say that metaphysical and theological claims cannot be rationally justified, it simply wouldn’t follow that such claims must be given the crude readings New Atheists often foist upon them, on pain of being empty verbiage. But it is, in any case, not correct to say that they cannot be rationally justified, which brings us to the second problem. That the methods of empirical science are rational does not entail that they are the onlymethods that are rational. In particular, and as I have pointed out many times, it is simply a blatant non sequitur to claim that science’s success in discovering those aspects of reality that are susceptible of strict prediction and control shows that those aspects exhaust reality. This is like a drunk’s insisting that because it is only under the streetlamp that there is light to look for his keys, it follows that the keys cannot be elsewhere and/or that there cannot be methods by which they might be sought elsewhere.
As I have also pointed out many times, the premises from which the historically most important arguments for God’s existence proceed derive, not from natural science, but from metaphysics and the philosophy of nature. They are, that is to say, premises that any possible natural science must take for granted, and are thus more secure than the claims of natural science, not less -- or so many natural theologians would claim. Obviously such claims are controversial, but the point is that to insist that metaphysical and theological assertions must be justified via the methods of natural science if they are to be worthy of attention is not to refute the metaphysician or theologian, but merely to beg the question against the metaphysician or theologian. Philosophical arguments are different from empirical scientific arguments, but they are no less rational than empirical scientific arguments.
Some readers might wonder how what I am saying here squares with what I said in a recent post about the danger of reifying abstractions. But there is no inconsistency. Naturally, I was not saying in the earlier post that abstraction per se is bad; indeed, I said the opposite. What I was criticizing was treating as substances (in the Aristotelian sense of that term) things which of their nature cannot be substances. Mathematical features of reality, for example, are aspects of substances and of relations between substances, rather than substances in their own right. Hence it is an error to treat the mathematical description of nature that physics gives us as if it were a complete description. Bodily organs like brains are also not substances but rather components of substances (namely of certain kinds of organisms) and intelligible only by reference to the complete organisms of which they form integral parts. Hence it is a category mistake -- deriving from a tendency first to abstract the brain from the organism and then fallaciously to treat it as a substance in its own right -- to speak (as some neuroscientists and philosophers do) of the brain or its components as if they “see,” “interpret,” etc., or to conclude that since free choice, purpose, etc. are not to be found at the neurological level of description, it follows that they don’t exist at all. These concepts apply in the first place only to the organism as a whole, and not to its parts.
The arguments of natural theology that I am defending do not commit errors like this. They abstract from experience, but they do not fallaciously treat accidents as if they were substances or parts as if they were wholes.
In any event, it is only by learning to think abstractly -- to engage in rational thought in its highest and purest form -- that you are ever going to understand metaphysical and theological arguments well enough to earn the right to criticize them. “New Atheists” -- by which, again, I do not mean all atheists, but rather the likes of Dawkins, Coyne, Myers and their innumerable online clones -- have not earned this right, precisely because they do not think at this high level. Indeed, they do very little thinking at all where metaphysics and theology are concerned, unless you count smartass remarks aimed at straw men followed by mutual high fives “thinking.” When dealing with one of these brainiacs, you might as well meet him where he’s at and channel Biff Tannen: