The first question, to repeat, is this: If our knowledge claims are true only under the condition that they are restricted to the realm of mere appearances, in what recognizable sense can they be described as objective, universal, and necessary?
Kant answers by drawing a very important set of distinctions and introducing some more terminology. In ordinary experience of the world, we frequently distinguish between what is real and what is not. An oasis is real. A mirage is not. The feel of a mattress beneath my leg is real; the sensations of so-called "phantom limbs" experienced by amputees are not in this sense real. They are real sensations, of course, but they do not reveal the presence of a real physical object. Rainbows are not real, in the same way that raindrops are. And so forth. So we may draw a distinction between the empirically real and the empirically ideal. Even if the entire experienced world is merely a realm of things as they appear to me in space and time and under the categories, nevertheless within that world the familiar distinction between the real and the merely ideal remains. And that, Kant insists, is all that is required for the validity of Newtonian Physics. Those laws tell us, with certainty and universality within the realm of experience, That all events have causes, and they tell us this prior to the experience of the events, which is to say a priori.
Now, if Kant is right, then the entire sphere of experience is, from a metaphysical point of view, merely ideal, for it is a sphere of things as they appear to us, not as they are in themselves. In short, the realm of experience is transcendently ideal, not transcendently real as Leibniz and other metaphysicians have claimed. Note, by the way, that this is one of those places where Kant writes "transcendentally" when he really means "transcendently." You can see why he would make that mistake. It is, in some sense, true that epistemologically speaking [which, you will recall, is what "transcendentally speaking" means, for Kant] things as they appear to us are merely ideal, for their empirical reality is conditioned upon their conforming to the subjective, mind-dependent forms of intuition and conception. So, to sum up, Leibnizean monads are transcendently real. Tables and chairs are transcendently ideal but empirically real. And hallucinations are empirically ideal.
Is this really all we are claiming when we say that Newton physics gives us in knowledge of the experienced world? Kant responds by turning the question back on the questioner. What else could you possibly want? he asks. You want to be able to distinguish a real oasis from a mirage. Very well, my theory allows you to do so. You want to distinguish a mere assemblage of "resembling instances," as Hume calls them, from a scientific law that predicts with certainty and universality what will happen in space and time. Very well, again, my theory allows you to do so. But you pound your fist on the table and demand something that is really real? What can that be, other than a genuinely solid table that is not an hallucination?
It might at this point occur to someone to wonder why, if Kant is correct, there is any point at all in continuing to talk about the unknowable transcendently real realm of Leibnizean monads. Isn't Kant simply like one of those Unitarian/Universalist pseudo-religionists who has given up a belief in God but still likes to go to a Sunday service now and again? There is a good deal of truth in this jibe, as we shall see later on. But Kant has one reason for keeping alive the possibility of thinking about a realm of which we can have no knowledge, namely that he believes the realm of unconditioned reality is the realm of moral agents bound by the Moral Law. Much, much later, I shall talk at some length about that side of Kant's philosophy. But first there is a good deal more to be said about his attempted defense of science against Humean scepticism.
The second question was: Where did those Categories come from? Once again, Kant operates at two quite different levels of philosophical explanation. The official story, from which he never deviates, is that the Table of Categories derives from the Table of Functions of Unity in Judgment, which is given to us by Logic. But as an answer this is twice-inadequate. First of all, the Logic Textbooks of Kant's day do not know this Table. It was invented by Kant both for reasons of architectonic neatness and because he needed some convenient hooks on which to hang an enormous amount of philosophical argument with which the Critique is filled. And Second, as we have seen, the transition from the first Table to the Second [which of course has a name too -- the so-called Metaphysical Deduction] rests on the hopelessly flawed argument that the two Tables must be parallel to one another because they memorialize two different activities of the same mental faculty, viz. the Understanding.
The real story is quite different from the official story, and very interesting philosophically. In a somewhat later section of the Critique, Kant will actually derive several of the Categories from an analysis of time-consciousness and the activity of synthesis that creates it. He will, in the ordinary sense of the term, deduce the Category of Cause and Effect. This derivation is the highpoint of the argument in the Critique, in my opinion, and it deserves a good deal of attention. We shall encounter it when we come to the section of the Analytic of Principles called the Analogies of Experience.
But first we must attend to the third, and most important, of the three questions we have imagined Hume posing to Kant, for it is in his response to this question that Kant reaches his greatest philosophical depths. What is synthesis? And in what way does synthesis transform a diversity or manifold of perceptions into a realm of phenomena governed by the laws of physics?
At this point, I encounter as an interpreter or commentator a problem from which there is no shrinking. In the First Edition of the Critique, Kant develops a detailed answer to the question, What is synthesis? It is to be found in Section 2 of "The Deduction of the Pure Concepts of Understanding," a passage that has been dubbed by commentators "The Subjective Deduction." As I shall argue at some length, the content of this section is the essential key to Kant's entire philosophy. But Kant was deeply ambivalent about it, because it is pretty obviously a psychological account of the way the mind works, and thus seems to be [indeed, as we shall see, is] open to the objection that it is grounded in observation, not philosophical analysis. Indeed, he was so ambivalent about the "Subjective Deduction" that he simultaneously repudiated it and embraced it in the Preface to the First Edition. At Axvii, Kant writes:
"This enquiry, which is somewhat deeply grounded, has two sides. The one refers to the objects of pure understanding, and is intended to expound and render intelligible the objective validity of its a priori concepts. It is therefore essential to my purposes. The other seeks to investigate the pure understanding itself, its possibility and the cognitive faculties upon which it rests; and so deals with it in its subjective aspect. Although this latter exposition is of great importance for my chief purpose, it does not form an essential part of it. For the chief question is always this: -- what and how much can the understanding and reason know apart from all experience? not: -- how is the faculty of thought itself possible? The latter is, as it were, the search for the cause of a given effect, and to that extent is somewhat hypothetical in character (though, as I shall show elsewhere, it is not really so."
That is, I think we can agree, a textbook case of ambivalence. So uncomfortable was Kant with the Subjective Deduction that when he came to rewrite the Deduction from scratch for the Second Edition, he omitted it completely from the text. And yet, and yet. I am absolutely convinced that we can only make sense of Kant's argument by taking the Subjective Deduction very seriously, and basing our entire interpretation of the Critique on its arguments.
We have now come to the very heart of Kant's undertaking, and of the interpretation I discovered fifty years ago. I shall therefore pause until tomorrow, for we need to be fresh and alert for what comes next.