A New Proof of the External World

A New Proof of the External World

It would be nice to be able to prove the existence of the external world (it would also be nice if there were a heaven). I am going to consider an argument that purports to do just that, not because I think it is sound, but because I think it is interesting. It is not simple like “I think, therefore I exist”; it isn’t anything like “It doesn’t think, therefore it exists”, which is not exactly watertight (more alcohol-tight, as in drunken). Nor did it occur to me while reading somebody famous and thinking that it might be an interpretation of that philosopher. As far as I know, it is spanking new–and rather infuriating; I think of it as an almost-proof. We can call it “the intelligibility argument”. In outline, it goes as follows: the world as represented by our experience and thought is not an intelligible world; but the real world is and must be an intelligible world; therefore, there must be another world external to our experience and thought. Let’s call the world represented by the human mind the “intentional world”: the claim, then, is that the intentional world cannot be all there is, because it is not fully intelligible; but reality must always be fully intelligible. There are no unintelligible real non-intentional worlds. The human intentional world has a lot of unintelligibility built into it, but then it cannot be real; so, there must be a further reality outside that world. To put it in more familiar terms, the world of the human imagination must be only part of a wider world that is not intrinsically unintelligible—which is our commonsense conception. If the imagined world were all there is, then reality would be inherently unintelligible (partly or wholly): but that cannot be; therefore, there must be more than this world.

There is a lot here to explain and I want to be brief. By an intelligible world I mean roughly one that is governed by laws which have some kind of necessity (this is sometimes called ontological rationalism). Nature must be uniform; it can’t be completely unpredictable and random. It can’t contain logical impossibilities. It can’t be intrinsically nonsensical. Classical mechanism provides a good model, though not the only one conceivable: chunks of matter conforming to Euclidian geometry and laws that could not be otherwise. This can be modified and extended in various ways, though not to the point of incoherence and madness. The world must work according to general principles that make sense. The intentional world is not intelligible in this sense: it is full of incoherence, illogicality, sheer nonsense, and breakdowns of natural law. I don’t mean anything exotic by this—it is a matter of common knowledge. Thus, dreams, fantasy fiction, Escher drawings, meaningless sentences, category mistakes, astrology, alchemy, visual illusions, imaginary scenarios of one kind or another. Take Escher drawings: these cannot depict possibly real things—there could not be a world composed of such things. Likewise, dream worlds are often impossible worlds, where things change lawlessly, illogically. The point is that the human mind is creative beyond the bounds of intelligibility. Therefore, our intentional world cannot be a real world. In fact, of course, we don’t suppose that it is: we assume that there is a world beyond this that obeys suitable laws—an intelligible natural world, free of absurdity. This world cannot be our world—the things we conjure up in our over-imaginative minds. It is thus part of our “conceptual scheme” that these two worlds must be kept apart, on pain of endowing reality with nonsense.

Suppose a creature lived in an intentional world of complete nonsense. It couldn’t be that this world was identical to the real world, or else reality would be nonsensical. The reality in which this creature actually lives is not objectively nonsensical; it just represents reality that way. We are like that: we know that reality cannot be as we imagine it—we know our intentional world is not the real world. But could our intentional world be all there is, with no reality beyond it? Could it all be a dream, even the non-dreaming world (as we commonly suppose it)? You might think the answer is no, because then reality would be unintelligible, consisting of nothing but our unintelligible intentional world. But that is too hasty: for we must not confuse our intentional world with our mental life–the world of our imaginative acts, our illusory perceptions, our episodes of dreaming, etc. It may well be that the world of the mind itself, as opposed to its intentional objects, is an intelligible world—a world governed by necessary intelligible laws. Psychology might be an intelligible natural science, while its intentional objects are the very antithesis of science. So, the world of our imagination is a real world, though what we imagine is not. There is then no valid argument to a distinct intelligible physical world; we already have a real coherent world in the shape of our own minds. A world containing only our minds is therefore metaphysically possible, no matter how unintelligible our minds may be in their intentional objects. After all, madness is real. It might be replied that we could adopt a different argumentative strategy: we could argue that such a mind would need a mind-independent physical brain to house it. That may be a sound move, but then we have dropped the intelligibility argument and replaced it with a new argument. This is why I said we only have an almost-proof. It is true that if the mind itself were not subject to intelligible laws, as well as its intentional objects, then we could apply the original argument—such a thing is metaphysically impossible, because reality cannot be intrinsically unintelligible. But the mind could be fully intelligible, even mechanistic, compatibly with being overrun by representations of the unintelligible. What we have is a proof that our intentional world is not the real world, so that some other world must exist to make it possible, either external to our mind (as we commonly suppose) or just the mind itself considered independently of its unintelligible contents. We know that reality cannot be the world as we imagine it, because that world is not a proper candidate for reality, by the intelligibility argument; but we have no proof that the further world must be the external world. It could, for all we have said, be the internal world, assuming that this is itself intelligible. It cannot be unintelligibility all the way down, but the bottom might be intelligible mental acts with unintelligible contents. Close, but no cigar. I suppose it might be objected that this position is suspiciously stipulative—we are just stipulating that the mind is a law-governed intelligible reality in order to avoid the inference to the real world as we commonly think of it. It has been conceded that our intentional world cannot be the real world, which was the main target of the argument. All we have left is the claim that the mind must be intelligible, i.e., governed by laws that make sense. We have no clear idea of what these laws might be; they are surely not the same as the mechanistic laws of matter. What are the laws governing dreams, illogical reasoning, and Escher-drawing perception? Might there be no such laws? Then we would be able to move to the desired (heavenly) conclusion that there must be an external world over and above the mind and its products. In any case, the dialectic has its own interest and charm, and that is all I promised.[1]

[1] It would be interesting to run the argument on mathematics or logic. We can agree that mathematics is inherently intelligible, and we can probably agree that it is possible to have unintelligible mathematical thoughts; but then mathematical reality cannot coincide with mathematical thoughts. Still, if unintelligible mathematical thoughts are psychologically intelligible, then we can’t use an intelligibility argument to infer that mathematical reality exists independently of mathematical thought, since we can fall back on psychological intelligibility to block the move to mathematical realism. The same structure applies to logic—and indeed to ethics. Ethical reality must be intelligible, but ethical thought may not be; therefore, ethical reality cannot be the same as ethical thought. Discuss.