Modal Categories and the Postulates

Kant argues that there are pure concepts of the understanding or categories. These are concepts that must be applied in experience in order for us to experience the world as we do.6 The application of a pure concept is not justified by experience, but by its being a prerequisite of having any ex- perience (of the kind we have) at all. One might say that these concepts are not acquired from any particular experience, but are “in us” prior to experience.7 There are four sets of three concepts; quality, quantity, relation and modality. The categories of modality are:

6_{Here take “we” to stand for, roughly, mentally mature creatures, human or similar,} with experience of an objective world. I will not address concerns regarding the status of infants and higher animals here.

7

This should not be taken to imply that pure concepts are to be understood as innate concepts. The point is not that we are somehow “born with” these concepts, but that these concepts play a peculiar role in our capacity for cognition and experience of the world.

Possibility—Impossibility Existence—Non-existence Necessity—Contingency

Kant does not explicate the categories immediately after their introduction in the Critique, but concentrates on their deduction, i.e. on establishing that they are applicable to experience even though they are a priori and not derived from experience. A fuller discussion of how we are to understand the modal categories appears soon after in the Postulates of Empirical Thought in General (A218–235/B265–288). This occurs as part of the Systematic Representation of all the Synthetic Principles of Pure Understanding. In other words, in this part of the Critique, Kant tries to systematically lay out those rules to which our cognitive faculties must conform when forming experience out of given input. The Postulates of Empirical Thought is the section in which he discusses those rules pertaining to the modal categories.

These rules are:

1. That which agrees with the formal conditions of experience, that is, with the conditions of intuition and of concepts, is possible.

2. That which is bound up with (zusammenh¨angt ) the material condi- tions of experience, that is, with sensation, is actual.

3. That which in its connection with the actual is determined in accor- dance with universal (allgemeinen) conditions of experience, is (that is, exists as) necessary.

(A218/B265—6).

They are then explained as follows:

The categories of modality have the peculiarity that, in deter- mining an object, they do not in the least enlarge the concept to which they are attached as predicates. They only express the relation of the concept to the faculty of cognition. Even when the concept of a thing is quite complete, I can still en- quire whether this object is merely possible or is also actual, or if actual, whether it is not also necessary. No additional deter- minations are thereby thought in the object itself; the question is only how the object, together with all its determinations, is related to understanding and its empirical employment, to em- pirical judgment, and to reason in its application to experience. Just on this account also the principles of modality are noth- ing but explanations of the concepts of possibility, actuality, and necessity, in their empirical employment; at the same time they restrict all categories to their merely empirical employment, and do not approve or allow their transcendental employment. For

if they are not to have a purely logical significance, analytically expressing the form of thought, but are to refer to the possibility, actuality, or necessity of things, they must concern possible expe- rience and its synthetic unity, in which alone objects of cognition can be given. (A219/B266–7)

These postulates are intended to explicate the rules or principles govern- ing our modal concepts. The first paragraph of the explanatory passage lays out the overall view: the modal status of an object (i) does not enrich the concept of that object, but rather (ii) is determined by a relation between the concept of that object and “the faculty of cognition” or to “understand- ing and its empirical employment, to empirical judgment, and to reason in its application to experience”. Note the two claims: there is the negative claim that modality is not a first-level property of objects, and the positive claim that modality of things concerns a relation between the concept of a thing on the one hand, and something to do with empirical experience and cognition of the world on the other.

The second paragraph emphasises that this is an account of modality as a feature of the empirical world, the world we experience. As such, conditions on the very possibility of this world of experience must be taken into account. If these concepts are to be about things in the world of experience, then they will have to respect conditions on the possibility of experience. If these conditions were not taken into account, we would end up with an account of another kind of modality. Later I will discuss Kant’s distinction between real and logical modality. He is alluding to such a distinction here. For an account of real, rather than merely logical, modality, we must take into account not only merely logical features of the concept of a thing, but also how it relates to conditions on experience.

A quick note on universal and formal conditions on experience: The formal conditions on experience are those conditions pertaining to formal features of experience, rather than the matter of experience. Regardless of the particular matter entering into the world of experience, if it is not of a certain form, it will not be counted as possible. E.g., one of Kant’s theses is that all objects of experience must be experienced in time, and all external objects of experience must be experienced in a spatial framework— non-spatiotemporal external objects will therefore not count as possible. The universal conditions of experience can be understood as those applying across the board: if something is to count as possible, it must conform to these conditions. It looks as though these conditions, formal and universal, match up insofar as they are both sets of conditions to which all objects of experience must conform. From this point on, then, I shall take them to be the same.

Another passage provides a summary of the overall view.

thetic. For the predicates of possibility, actuality, and necessity do not in the least enlarge the concept of which they are affirmed, adding something to the representation of the object. But since they are none the less synthetic, they are so subjectively only, that is, they add to the concept of a thing (of something real), of which otherwise they say nothing, the cognitive faculty from which it springs and in which it has its seat. Thus if it is in connection only with the formal conditions of experience, and so merely in the understanding, its object is called possible. If it stands in connection with perception, that is, with sensation as material supplied by the senses, and through perception is de- termined by means of the understanding, the object is actual. If it is determined through the connection of perceptions according to concepts, the object is entitled necessary. The principles of modality thus predicate of a concept nothing but the action of the faculty of cognition through which it is generated. (A233– 4/B286–7)

Again we have the negative claim that modal concepts do not add to the concept of an object, alongside the positive claim that they concern a re- lation between that concept and our cognitive faculties, i.e. the conditions they impose upon the world. These principles are not “objectively syn- thetic”, but are subjective. They do not concern a property an object has on its own, independently of any subject, but rather they concern the ob- ject as it relates to some “cognitive faculty”. What is important here is not so much the particular faculty Kant says is relevant, but the connection between possible experience and our cognitive faculties. Kant is known for having rather a mania for system, to the detriment of some of his ideas. The balance of different modalities being seated in different faculties looks suspi- ciously tidy. The key point is that conditions of experience are said to stem from our cognitive faculties. If there are constraints upon experience, then according to Kant, they have something important to do with our cognitive constitution. So when he writes about our cognitive constitution here, we are to understand that the key thought concerns the conditions on experi- ence. Possibility is mere compatibility with these conditions. Actuality is straightforward empirical experience. Necessity is what follows from given experiences and the laws apparent in those conditions. And no object could be possible, actual or necessary in the absence of some subjective conditions on experience. In some sense, yet to be explained, modality looks like it may turn out to be mind-dependent (see section 4.3.4).