Mortimer Adler says in the introduction to this book, quoting from Thomas Aquinas, that often the most pernicious errors in philosophy are not large, obvious mistakes in claims or conclusions, but "little errors in the beginning". I'm well aware of the irony of pointing out a similar mistake in his own book, although in this case the little error comes not at the beginning but at the end, at least as the discussion is ordered in the book. But the error is an important one (more accurately, it is a failure to explicitly state a key assumption, but since when explicitly stated that assumption is seen to be one with notorious difficulties in philosophy, I think it qualifies as an error), so I think it's worth discussing here.
Adler also says in his introduction that a more accurate title for the book would have been "Ten Subjects About Which Philosophical Mistakes Are Made" (he chose the book's actual title for what I agree are obvious reasons of "catchiness"), and the main body of the book is simply a review of the ten subjects, the mistakes made in each of them, and the insights and distinctions necessary to correct the mistakes. The book is not meant to be a comprehensive treatment of Adler's own philosophical or metaphysical views, and since he does not present arguments for the corrections he gives to the various mistakes (he says he depends on the reader to discern that "the corrections have the ring of truth"), there is obviously the danger that a critical premise or observation will be left out. To Adler's credit, he recognizes this possibility, and in a number of places he refers the reader to more detailed treatments of important issues in his other works.
There is one place, however, where he does not do this, even though, as we shall see, there is an important unstated premise that underlies his treatment of an issue. That issue is the issue of existence--briefly, the question is what it means to say that an object "really exists", and in particular, whether we are justified in saying that we ourselves, human beings as persons with free will and moral responsibility, "really exist" in the sense necessary to ground our common sense view of ethics, laws, and justice. He treats this as the last of the ten subjects about which philosophical mistakes are made, and this seems surprising to me, since at first sight it certainly appears that the question at issue is one which needs to be answered before we can even discuss any of the other issues discussed in the book. For example, the first subject of the ten is "Consciousness and Its Objects", but surely, if we have not yet resolved the issue of our existence as conscious beings, talk about consciousness and its objects is premature.
Be that as it may, Adler says that the philosophical mistake about existence that is made in modern thought is the mistake of reductionism. He quotes from a lecture that Sir Arthur Eddington, the British astronomer, gave on "The Nature of the Physical World", in which he claimed (or seemed to claim) that solid objects, such as the table in front of him, were really "illusions"--the only "real" things present were the atoms that made up the table. This lecture of Eddington's is a famous one, and there are a number of possible interpretations of what he was saying. One of these is indeed the "radical" reductionism that Adler attributes to him, but it is not the only one.
Let's look at the example that Adler and Eddington both use, that of a table. Modern science tells us that a table is made up of atoms--to be more precise, modern science tells us that, if we pick out a certain portion of the physical world, to which we would normally attach the name "table", there are two ways of looking at it: as a single "solid object" (the table), or as a collection of a humongous number of atoms of many different elements. Now granted that there may be some radical reductionists out there who would agree that these two ways of looking at a table are inconsistent (this is how Adler interprets Eddington's statement that the view of the table as a single thing is an illusion), still this does not exhaust the possibilities. And it is particularly surprising that Adler does not mention one of them here, since it was stated by him back in Chapter 3, in his discussion of words and meanings. There, he discusses the problem of how one and the same physical object can be referred to by multiple common nouns: for example, we can refer to one and the same creature as a "dog", "mammal", or "quadruped". Adler sees no problem with this, but he does not seem to realize that the same idea can be applied much more broadly.
For example, clearly we can take the same line with the table: we can simply say that "table" and "large conglomeration of atoms in such-and-such configuration" are different descriptions of the same piece of physical reality, just as "dog", "quadruped", and "mammal" are different descriptions of the same piece of physical reality. We are simply recognizing the fact, one of the great discoveries of physical science, that there is more than one way of looking at physical objects: we can look at them as unified wholes (this is justified because under a wide range of conditions they do indeed act as unified wholes--tables don't come apart into their constituent atoms without something drastic being done to them) or we can look at them as collections of atoms with certain properties and interactions between them. Both of these descriptions are valid descriptions, and the different perspectives they offer us are no more inconsistent than the different perspectives offered by looking at a dog as a quadruped and looking at it as a mammal.
So there is a simple way of avoiding the apparent problem with taking Eddington at face value; we do not have to believe that objects like tables are "really" illusions in order to accept what science tells us about them. We can simply view these as two different, complementary, but consistent descriptions. This would correct the mistake of radical reductionism, by admitting that tables and other macroscopic objects really exist, as our common sense claims they do, without having to throw away our hard-won understanding of the microphysical objects and interactions that account for the existence and properties of those macroscopic objects.
But Adler does not even mention this possibility, and this is his "little error in the beginning", for his failure to consider it forces him to tie himself in knots trying to explain a putative "contradiction" that is not really a contradiction at all. Not only is he forced to make obviously implausible claims about macroscopic parts of objects--for example, he has to claim that a table leg is only a "virtual" table leg when it is attached to a table, and only becomes a "real" table leg when it is broken off and separated--but also he has to misconstrue what quantum mechanics tells us about atoms and subatomic particles. Here again he uses the term "virtual", but in an even more problematic way than before, since that term has a precise meaning in quantum mechanics which is quite different from the one Adler gives it--the atoms and subatomic particles that make up a table are not "virtual particles" in the precise quantum sense of the term. Adler could be using the term as his own "technical term", unrelated to the quantum mechanics term, but if so, he should say so; instead, by quoting Heisenberg, he invites the implication that he means the term in its usual scientific sense, which is simply wrong in this connection.
All these errors could have been avoided if Adler had simply adopted the line I have described, that the common-sense description of a table and the scientific description are simply different ways of looking at the same thing, both valid, and each consistent with the other. Why does Adler not do this, or even mention the possibility? I can't say for sure, of course, but I can come up with one plausible conjecture. After all, the case Adler is really concerned about when he discusses the question of existence, as I said before, is not the case of tables and chairs, but the case of human beings as free-willed, morally responsible persons. When that case is phrased in terms of the "different descriptions" alternative I suggest, it does sound less intuitively desirable than the case of a table does. Let's look at it to see why.
In this case, the two different, valid, and consistent descriptions are: (1) this piece of physical reality is a conglomeration of atoms in a certain (very complex!) configuration, which gives it certain (very complex!) properties, and (2) this piece of physical reality is a free-willed, morally responsible human being. In Chapter 7 of the book, where Adler deals with the question of free will, his description of the positions of the two parties in the dispute (the "free will" party and the "determinism" party) sounds very much like the two descriptions I just gave of a human being. And Adler's point in Chapter 7 is that the issue between the two parties is not joined: that neither one can convince the other because they are really talking about two different issues, based on two different sets of premises. This sounds very much like saying that the two descriptions I just gave of a human being are somehow not consistent, which would invalidate my suggestion for avoiding all the problems about existence that Adler gets himself into.
Further support for this can be found in Chapters 1 and 2, when Adler is discussing the intellect, and stating his view that it is a separate capacity of the human mind from the sensory/perceptual capacity. At one point, he states bluntly that the intellect, unlike the senses and perception, is not explicable in terms of the physical constituents of the brain. Given this, it is quite reasonable to suppose that Adler would reject the line I suggested above because he would say that it is simply not possible for one and the same thing to be both a free-willed, morally responsible person and a conglomeration of atoms. Therefore, there is no way the two descriptions I gave above could possibly be consistent.
But note how strong this position is: indeed, it is at least as strong as its opposite, the "radical" reductionism that Adler reads into Eddington's lecture on the table. The radical reductionist says, in effect, that there is no way one and the same piece of physical reality can be both a table and a conglomeration of atoms. Since the science in which he believes tells him that the conglomeration of atoms is real, he is forced to view the table as an illusion. But Adler would have to say that, since the moral philosophy in which he believes tells him that a human being really exists as a free-willed, morally responsible person, then the scientific view of a human being as a conglomeration of atoms must be, in some sense, an illusion.
If this is true (and I do not see any other way of making sense of his discussion of existence in Chapter 10), then this is indeed, as I said at the start of this review, a key assumption that underlies his position, but is never explicitly stated. It is worth noting, in light of Adler's stated views about the wisdom of ancient philosophers (often contrasted with the ignorance and hubris of modern philosophers--the Epilogue to this book, "Modern Science and Ancient Wisdom" is a good example), that, although the metaphysics implied by this assumption was not explicitly stated until modern times (as we will see in a moment), the assumption itself was one with which the ancient philosophers that Adler admires, Socrates, Plato, and Aristotle, would probably have agreed. This is because it is a natural consequence of the view that human beings are unique among all biological species in having attributes, such as intellect, which the ancient Greeks called "divine", and which Adler, even if he does not explicitly draw the theological implications, evidently considers to be very special, special enough to justify a special metaphysics to ground it.
This metaphysics is a familiar one in the history of philosophy, and the name for it is "dualism". Dualism is the view, first enunciated explicitly (so far as I know) by Descartes, that, in effect, there are two kinds of "stuff", mind and matter. Matter is what makes up the physical world, and what our science studies; it is the "conglomeration of atoms" in the above descriptions I gave. Mind is what, on Adler's view, would account for human intellect, reason, free will, and moral responsibility, and it is intrinsically inexplicable in terms of the operations of matter--it is, by definition, something different from matter. This is not the place to discuss the weaknesses of dualism as a metaphysics, but it is fair to say that it suffers from well-known difficulties to which no one has ever found a satisfactory answer. Apparently Adler either thinks he has (and perhaps intends references to his other books, The Difference of Man and the Difference it Makes and The Angels and Us, to serve as pointers to his answer), or has failed to consider the issue.
In any case, it should be clear by now what I think my suggested answer to this issue has going for it: that it is clearly more inclusive than either of the extreme positions. Rather than be a radical reductionist or an out-and-out dualist, why not stick with the inclusive position--that, yes, we can describe one and the same piece of reality as both a conglomeration of atoms and a free-willed, morally responsible human being? Note that this is all that is really required to support Adler's belief in moral philosophy; it is not necessary to insist that our description of ourselves as free-willed, morally responsible human beings is the only valid description, just that it is a valid description (though not necessarily the only one). If this is so, why insist on the "radical" view? Why not, instead, adopt the inclusive view, at least provisionally, and see how far it takes us? It may never take us to a complete and final answer--both dualism and radical reductionism may always remain as "in principle" possibilities; we may never be able to rule either one out with 100% confidence--but at least we will be keeping an open mind.
Now of course "keeping an open mind" is not always a virtue, and I don't know if Adler would agree that it is the best policy to adopt in this case. But in cases like this, where our intuitions and our scientific knowledge clash so violently, it certainly seems like a wise policy--particularly if, as I said just now, the middle-of-the-road view is sufficient to ground what we really care about, our system of ethics, morality, and justice. Why insist on arguing over abstruse points of metaphysics when they don't matter to the real issue? But this is a view that neither the dualist nor the radical reductionist can adopt, because their whole position consists in ruling out the opposite position by fiat. This may be fine if you're certain you're right. But what if you're wrong?