SEoP Kant

 

3.4.1 The Unknowability of Things in Themselves

Kant is committed to both of the following theses:

(Existence) There are things in themselves.

(Humility) We know nothing about things in themselves.

While these are not, strictly speaking, incompatible, they are in tension, for Humility appears to remove any warrant Kant might have for asserting Existence.

But it gets worse for the traditional view. Kant does not merely claim that things in themselves exist, he also asserts that,

(Non-spatiality) Things in themselves are not in space and time.

(Affection) Things in themselves causally affect us.[31]

Many of Kant’s early readers concluded that Kant’s philosophy is inconsistent: he claims that we cannot know the very assertions he makes about things in themselves. Kant’s own theory renders itself unknowable.[32]

It would be over-hasty to suggest that each of these three problems—how to square Humility, with Non-Spatiality, Affection, and Existence—are on a par. Since Non-spatiality makes only a negative claim, it may be easier to make it consistent with Humility. For instance, at B149 Kant writes:

it is not yet a genuine cognition if I merely indicate what the intuition of the object is not, without being able to say what is then contained in it.

This suggests that, while Kant’s usually unqualified statements of our ignorance of things in themselves (they are “not cognized at all” A30/B45), his considered view might be more qualified: we know nothing of the positive properties of things in themselves.[33] But Affection looks especially difficult to square with Humility (see Hogan 2009 and Stang 2013).

3.4.2 Things in themselves as causes

The issue of things in themselves affecting us raises another problem for Kant’s theory, for Kant also argues that categories like cause-effect cannot be meaningfully applied to things in themselves. Without an intuition “[the category] has no sense, and is entirely empty of content” (A239/B298). Since things in themselves cannot be intuited, categories (including cause-effect) have no sense or content when applied to things in themselves. Jacobi and others thought this was yet another inconsistency in Kant’s philosophy: he denies that categories can be applied to things in themselves, but then he applies the category cause-effect to them!

However, one has to be careful in interpreting Kant’s denial of “sense” or “meaning” to categories as applied to things in themselves. It is tempting to read this as meaning that the thought of things in themselves falling under categories is literally nonsense, but there is textual evidence that Kant is making a weaker point: thinking of things in themselves under the categories has no cognitive sense, i.e., in making such judgments we do not cognize anything. For instance,

[…] the categories are not restricted in thinking by the conditions of our sensible intuition, but have an unbounded field, and only the cognition of objects that we think, the determination of the object, requires intuition; in the absence of the latter, the thought of the object can still have its true and useful consequences for the use of reason […] (B166n)[34]

We can think of any objects whatsoever using the categories. In fact, this is unavoidable; the categories are the most basic concepts of objects in general, so we cannot think about anything whatsoever without using some categories to do so. But in thinking about the things in themselves using categories we do not thereby (a) know that there are things in themselves falling under the categories or (b) even that it is possible for there to be things in themselves falling under the categories. The strongest form of Jacobi’s objection—that Kant’s view entails that the categories cannot be applied, even in thought, to things in themselves—may rest on a misunderstanding (cf. Van Cleve 1999: 137; Adams 1997: 820–1). This still leaves, though, the pressing problem of how, given Kant’s Humility doctrine, he could have any epistemic warrant for making the various substantive claims he does about things in themselves (Existence, Non-spatiality, Affection).

3.4.3 The Problem of Affection

Jacobi raises yet another problem about Kant’s theory of experience. He notes Kant’s definition of sensibility as the capacity “to receive representations through the manner in which we are affected by objects” (A19/B33) and poses a dilemma: are the objects that affect our sensibility appearances or things in themselves? They cannot be things in themselves, Jacobi argues, because that would involve applying the categories to things in themselves. And they cannot be appearances, because appearances exist in virtue of the very experiences they are (allegedly) causing. He concludes that Kant’s system is inconsistent (Jacobi, Werke, vol. II, 291–310; Fichte raises the same objection in the Second Introduction to the Wissenschaftslehre; cf. Fichte, Werke I, 488).

We have already discussed the argument of the first horn of Jacobi’s dilemma: we can think but not know that things in themselves causally affect us. But what about the second horn? Hans Vaihinger concisely explains Jacobi’s argument:

Or one understands by affecting objects the objects in space; but since these are only appearances according to Kant, and thus our representations, one falls into the contradiction that the same appearances, which we first have on the basis of affection, should be the source of that very affection. (Vaihinger 1881: vol. 2, p. 53)

“First” here does not refer to temporal priority, but to metaphysical priority: if p is true in virtue of q, then q is “prior” to p. Jacobi and Vaihinger assume that appearances exist in virtue of the contents of our experience of them:

(Trans. Idealism) If x is an appearance, then x exists in virtue of the fact that subjects experience x.

If we are empirically affected, though, it follows that:

(Empirical affection) For some x, x is one of the causes of subjects’ experience of x.

For instance, this computer is one of the causes of my current experience of it. But these assumptions are inconsistent if we assume the following plausible principle:

(Exclusion) If x exists in virtue of the fact that p, then x cannot be even a partial cause of the fact that p.

Intuitively, this principle says that no object can be even a partial cause of the very fact in virtue of which it exists; if it were, it would be a partial cause of its own existence. In the context of Kant’s theory of experience, it means that appearances cannot “reach back” and cause the very experiences in virtue of which they exist. From the 1780s until today, many have taken this problem to be fatal to Kant’s theory of experience.[35]