At this point in Kant's story, something rather surprising and very important happens. In a word, Time steps forward and takes pride of place over Space. This shift is wrapped up with Kant's very difficult but crucially important theory of Inner Sense. Until now, as I have tried to make clear, Kant's focus has been on the mind-dependent form of Space that is imposed on sensations as they are produced in the mind by the effects of things in themselves on us. In the Dissertation, where his primary concern is with the status of Geometry, space is placed center stage, and time is added almost as an afterthought. The same relative importance is accorded to them in the first major section of the Critique, the Transcendental Aesthetic. Now, however, we find that in the Deduction, Kant's discussion is all about time consciousness, and space does not figure significantly at all in the argument. There are two reasons for this switch, and each of them is of the very greatest importance. At the risk of causing your eyes to glaze over, I am going to discuss each of these reasons at some length. [I warned you that Kant is hard. Keep in mind that we are still only discussing the first 20% of the text!]
Descartes' expository tactic in the Meditations was to raise doubts about all of the knowledge claims handed down to us by his predecessors, until, in the Second Meditation, he comes to one that he cannot doubt: I am, I exist. He then undertakes, rapidly and with rather flimsy arguments, to reinstate the received wisdom -- the existence of God, the existence of a world of substances in causal interaction with one another, and so forth. Since the Cogito argument seems indubitable, whereas everything following it is a bit iffy, the effect of Descartes' tactic is to create an extremely unbalanced relation between self-knowledge and knowledge of independent reality. I can be absolutely certain, Descartes tells us, of my own existence as a real substance, a "thing that thinks," in Descartes' famous phrase, whereas I cannot be quite so certain of the reality and existence of anything else. To use a phrase that became popular in Anglo-American philosophy back when I was a boy, the mind, Descartes is telling us, has "privileged access" to its own being and nature.
Now, Kant rejects this view entirely. He has given up the claim that we can have knowledge of the existence and nature of independent reality, and that includes any knowledge of the self as well as of God or Leibnizean monads. To paraphrase Kant [or perhaps quote him -- these phrases is burned into my mind], the self knows [even] itself not as it is in itself but only as it appears to itself. You can see why this would be important to Kant. If he accepts Descartes' account of the privileged access of the mind to its own existence and nature as a thing in itself, then he will be forced to acknowledge that all the rest of our knowledge claims -- those of science -- are. as Hume so powerfully argues, unwarranted. If he is to establish Newtonian Physics as genuine knowledge, albeit of Appearances, he must insist that self-knowledge is no better, epistemologically, than knowledge of objects. [For those of you who are real philosophy buffs, it is interesting to note that in this argument, Kant is siding with Spinoza rather than with Descartes. I am not sure he knew that, however.]
According to Kant, the mind knows itself in just the same way as it knows objects -- through the affection of its sensibility and the generation thereby of a manifold of intuition. The difference is that it is the Inner Sense that is affected, not the Outer Sense, and the manifold of intuition thus generated has imposed upon it the form of time rather than the form of space.
What is the story Kant tells us about this complex process? Here it is in as simple and comprehensible a form as I can manage.
(1) Things in themselves in some way affect my sensibility, with the result that there is generated a diversity of sense contents on which a spatial form has been imposed. [This sounds very much like a causal statement, but of course it cannot be, according to Kant, because the concept of cause and effect is one of the mind dependent categories, and hence only applies to things as they appear to us. Kant really should simply begin with the given fact of a diversity of sense contents, but he reveals here the lingering effects on him of his pre-Critical beliefs.] This is the Synthesis of Apprehension in Intuition.
(2) The mind, in an attempt to bring the diversity or manifold of sense contents to consciousness, does something to them. It synthesizes them. More precisely, it reproduces them, using its capacity for recalling in imagination what has been presented in sense. In the act of so doing, the mind affects itself, or more precisely affects its Inner Sense, and the result is that the sense contents thus recalled are recalled in a temporal order, according to the rule that is being invoked by the mind. This is the Synthesis of Reproduction in Imagination.
(3) Having thus reproduced its spatially organized sense contents in a temporal order according to a rule, the mind now reflects on what it has done and recognizes that the order in which it has recalled its sense contents is actually in conformity with a concept, which, you will recall, is always "something universal which serves as a rule." This is the Synthesis of Recognition in a Concept.
Kant actually gives an example of this process [something he does not often do! When he does, grateful readers fall on it like thirsty desert wanderers coming upon an oasis. Another example of course is the Four Examples of the Categorical Imperative in the Groundwork of the Metaphysics of Morals.] The example is counting. When I count a group of objects, he notes, I do not simply count "one, two, three, ..." Instead, to put it crudely and explicitly, I count: This is one, and this a second, which I am counting after having labeled the first one "one," and this is a third, which I am counting after I have labeled the first one "one" and the second one "two," and so forth. In short, in the process of counting [reproducing each item in imagination], I am also conscious of carrying out this activity in conformity with the rule for counting [Recognition in a Concept]. The result is the imposition of a unity on the multiplicity of objects -- a unity that they possess not in their own right, as it were, but as a consequence of having been ordered according to a rule. I thus achieve a unity of my consciousness of the several objects.
Sometimes, of course, I do not follow the rule. Little children, who have learned the names of the numbers but not yet the rule for counting, can sometimes be heard saying "one, seven, two, five, three, four, twenty-eleven, etc." And when I am counting, say, a pack of cards, if I get distracted, I lose count -- that is, I lose my unifying awareness of having carried out an iterated process in accordance with a rule. When I take my morning four mile walk, for example, I sometimes count steps, as a way of dealing with the boredom of the walk, but if I pass another person and say hello, as I usually do, I may lose count, and no longer know whether I am up to three hundred seventy or three hundred eighty.
So, what is synthesis? It is reproduction in imagination according to a rule. The Unity of Consciousness that is, according to Kant, the fundamental starting point of all philosophical reasoning, is the product of this activity of reproduction in imagination of a diversity of given sense contents. I can know, a priori, that the categories will find application within the sphere of experience because they are the rules in accordance with which that experience is produced through the unifying rule governed activity of synthesis.
What then are the categories? [In this entire complicated account, Kant has not so much as mentioned any of the twelve Categories in his Table by name.] As you might by now expect, the answer is complicated. We shall tackle it tomorrow.