Kant, Immanuel (1724–1804)

3. The Inaugural Dissertation of 1770 and the problem of metaphysics

Kant’s Inaugural Dissertation of 1770 consolidated many of the gains he had made during the 1760s and introduced a fundamentally new theory about the metaphysics and epistemology of space and time which was to remain a constant in his subsequent thought, but also left open crucial questions about the source of our most fundamental concepts. Although Kant hoped to proceed quickly to his projects in the philosophy of science and in moral and political theory, it was to take him all of the next decade to answer these preliminary questions.

Taking up where Directions in Space left off, Kant begins the dissertation with the distinction between intuitions (singular and immediate representations of objects) and concepts (general and abstract representations of them) as distinct but equally important elements in the ‘two-fold genesis of the concept [of a world] out of the nature of the mind’. The intellect (Kant does not yet divide this into understanding and reason) provides abstract concepts, under which instances are subordinated; the ‘sensitive faculty of cognition’ provides ‘distinct intuition[s]’ which represent concepts ‘in the concrete’ and within which different parts may be coordinated (2: 387). Kant goes on to claim that ‘whatever in cognition is sensitive is dependent upon the special character of the subject’, that is, the knower, so that sensation, through intuitions, represents things ‘as they appear’ (phenomena), while the intellect, through concepts, represents things ‘as they are’ (noumena) (2: 392). Kant then presents the ‘principles of the form of the sensible world’: time and space are the forms of the intuition of all objects (time is the form for all representation of objects, inner or outer, while space is the form for the representation of all outer objects) which do not arise from but are presupposed by all particular perceptions; they are singular rather than general, that is, particular times or spaces are parts of a single whole rather than instances of a general kind; and they must each be ‘the subjective condition which is necessary, in virtue of the nature of the human mind, for the co-ordinating of all things in accordance with a fixed law’, or a ‘pure intuition’ rather than ‘something objective and real’ (2: 398–400, 402–4). Only thus can we explain our knowledge of both these general claims about space and time as well as particular claims about their structure, such as the theorems of geometry (2: 404). In other words, we can explain the certainty of knowledge about space and time only by supposing that it is knowledge of the structure of our own minds, and thus of how objects appear to us, rather than knowledge about how things are in themselves. This necessarily subjective origin and significance of certainty, which Kant was later to name ‘transcendental idealism’, is the foundation for the active role of the human mind in knowledge of the world.

Kant has little to say about the source of intellectual concepts, but continues to believe that they give us knowledge of how things are independently of the structure of our own minds. His main claim, still Leibnizian, is that in order to conceive of things as genuinely distinct substances, yet as collectively interacting in a single world, we must conceive of them as contingent beings all depending upon a single necessary being (2: 407–8). Kant then argues that metaphysical error arises when the principles of sensitive and intellectual cognition are confused, but more particularly when ‘the principles which are native to sensitive cognition transgress their limits, and affect what belongs to the intellect’ (2: 411) – the opposite of what he will argue later when he claims that metaphysical illusion arises from thinking that human reason can reach beyond the limits of the senses (see §8). Finally, Kant introduces as mere ’principles of convenience’ the principles of universal causation and of the conservation of substance as well as a more general ‘canon’ of rationality, that ‘principles are not to be multiplied beyond what is absolutely necessary’ (30, 2: 418). A better account of these principles will occupy much of Kant’s later work (see §7).

Early readers of Kant’s dissertation objected to the merely subjective significance of space and especially time, but Kant was never to surrender this theory. What came to bother him instead was his inadequate treatment of metaphysical concepts such as ‘possibility, existence, necessity, substance, cause, etc.’ (2: 395). In a famous letter of 21 February 1772 to Marcus Herz (10: 129–35), Kant claimed that the ‘whole secret’ of metaphysics is to explain how intellectual concepts which neither literally produce their objects (as God’s concepts might) nor are merely produced by them (as empirical concepts are) nevertheless necessarily apply to them. But Kant did not yet know how to answer this question.

His first progress on this issue is found in fragments from 1774–5 (Reflections 4674–84, 17: 643–73). Two key ideas are found here. First, Kant finally formulates the problem of metaphysics as that of ‘synthetic’ rather than ‘analytic’ propositions: how can we know the truth of propositions in which the predicates clearly go beyond anything contained in their subject-concepts but yet enjoy the same universality and necessity as propositions which are mere tautologies, whose predicates are contained in their subject concepts (17: 643–4, 653–5)? Second, Kant here first states that the answer to this question lies in recognizing that certain fundamental concepts, not just the intuitions of space and time, are ‘conditions of the concrete representation [of objects] in the subject’ (17: 644) or of the unity of ‘experience in general’ (17: 658). Kant’s idea is that in order to ground any determinate ordering of either subjective or objective states in temporal succession, we must use the concepts of substance, causation, and interaction, and that these must therefore be categories which originate in the understanding just as the pure forms of space and time originate in the sensibility.