of experience can be structured and organised. But what is meant precisely by formal principles? What are their features? According to Kant, a principle is that which contains the reason of a relation. While the principle of the form of the intelligible world is an objective cause, the world of phenomena, i.e. of our experience, has a subjective principle only. The latter is regarded as a law of the mind (animo), according to which things appear as if they belong necessarily to a whole. This principle has no validity for objects that cannot be objects of our possible experience. More specifically, Kant states that there are two formal principles of the sensible world: space and time.←48 | 49→
“These formal principles of the phenomenal universe are absolutely primary and universal; they are, so to speak, the schemata and conditions of everything sensitive in human cognition. I shall now show that there are two such principles, namely, space and time.” (AA II, p. 398)56
In the above-mentioned passage, ‘schema’ assumes a new significance: it does not refer to something unclear, nor does it mention the divine understanding of the Dilucidatio. Instead, it refers to the conditions of sensibility and human knowledge, namely the formal principles of space and time, which are provided with characteristics, which will be reechoed in the Critique of Pure Reason.
Since the last occurrence of the term ‘schema’ is found in reference to the elucidation of the forms of space and time, I will briefly introduce the characteristics of these forms. Kant first clarifies the notion of time, because it is more general than space: each experience, is at least temporal (“internal” such as emotions), while some are also spatial (“external” for instance: representations of objects and events). Because time is the most general condition of experience, it does not derive from the senses, but it is a presupposition of them and for this reason it is non-discursive, in opposition to thoughts, which are abstract and derivative.
Moreover, time must be one, singular, identical, and homogeneous (quantum continuum) in order to explain the experiences of succession and simultaneity of the material elements that are related. Time is the possibility of this relation in itself and for this reason, time cannot be regarded as belonging to the same level of sensible features. In conclusion, time is defined as a pure subjective intuition (and not a discursive concept), which does not belong to nor derives from matter. The reference to time as “subjective” might be misleading: it seems, that time identifies a sort of natural human capacity as if Kant is providing a naturalistic or anthropological explanation of the process of experience. However, the allusion to time as a pure intuition suggests that such an interpretation has to be put aside. Time, then, is the condition of all sensible experience, or the universal form of all phenomena, through which they are perceived as existent and can be coordinated. It is this feature, which clearly and deeply differentiates Kant’s approach from, say, the empirical explanation of the process of knowledge by Johann Christian Lossius. In his Physischen Ursachen des Wahren of 1775 Lossius states that the principles of logic can be understood only through the reference to the organs that are implied in the production of ideas. This point of view is similar to that of Tetens, from which Kant explicitly distances himself:←49 | 50→
“Tetens investigates the concepts of pure reason merely subjectively (human nature), I objectively. The former analysis is empirical, the latter transcendental” (AA XVIII, p. 23)57
Similarly to time, space also cannot be regarded as a concept, as something induced from experience but rather as a law, a function, presupposed in each perception as a condition of its organisation. As anticipated, here Kant refers to space as ‘schema’:
“Space is not something objective and real nor is it a substance, nor an accident, nor a relation; it is, rather, subjective and ideal; it issues from the nature of the mind in accordance with a stable law as a schema, so to speak, for co-ordinating everything which is sensed externally.” (AA II, p. 403)58
Kant here expresses himself no further on ‘outline’ (the English translation of the Latin ‘schema’), which will be later investigated in more detail in the Critique of Pure Reason. However, from the content of the Dissertation, it is possible to argue that it might be regarded as a condition of the order of perception, a ‘schema’ in the sense of a pattern that provides unity and coordination and that space and time are linked to sensibility but do not derive from it.
Besides the above-mentioned occurrences of ‘schema’, there is another passage in the Dissertation which is of great interest for my inquiry:
“But pure (human) intuition is not a universal or logical concept under which, but a singular concept in which, all sensible things whatever are thought, and thus it contains the concepts of space and time. These concepts, since they determine nothing as to the quality of sensible things, are not objects of science, except in respect of quantity. These concepts, since they determine nothing as to the quality of sensible things, are not objects of science, except in respect of quantity. Hence, PURE MATHEMATICS deals with space in GEOMETRY, and time in pure MECHANICS. In addition to these concepts, there is a certain concept which in itself, indeed, belongs to the understanding but of which the actualisation’ in the concrete requires the auxiliary notions of time and space (by successively adding a number of things and setting them simultaneously side by side). This is the concept of number, which is the concept treated in ARITHMETIC.” (AA II, 397)59←50 | 51→
In these lines, Kant does not refer to schemata but to a number, which will be one of the particular, transcendental schemata exposed in the Critique of Pure Reason. This reference is important because it alludes to the way in which schematism will be developed: namely, the concepts of the understanding (such as number), can be actualised through time (and space).
After considering these references to the notion of schema, it is possible to synthesise its significance as the following: schema is no more a metaphysical concept (as it was presented in the Dilucidatio), but rather it obtains a more epistemic significance. It refers to the forms of sensibility, which are necessary conditions for providing the material elements of experience with organisation, thus explaining the possibility of experience and knowledge. This characterisation of space and time as schemata (or “quasi” schemata, as if Kant is using the noun schema without a proper definition) as conditions shares similarities, but also differences, with the doctrines of the Critique of Pure Reason: on the one hand, space and time are defined in the Transcendental Aesthetic as conditions of the possibility of the intuition, on the other, they become defined as pure intuitions and not as schemata (that will have a different function as illustrated in the Transcendental Logic). Nevertheless, there are passages in the Critique of Pure Reason in which they are still regarded as conditions (KrV A140/B179), although in a different sense as the forms of intuitions of space and time.
The value of the Dissertation might lie precisely in the doctrine of space and time and in their definitions as forms, schemata, which provide a solution to an important debate of the time, namely the conflict between empiricism and rationalism. However, Kant’s theory has its limits, which the author himself soon becomes aware of and which lead him to write the Critique of Pure Reason.
To underline both the novelties and the limits of Kant’s doctrine of space and time in the Dissertation and to understand why he will develop his theory of form and schema in the Critique of Pure Reason, it is helpful to refer to the main theories that he encountered concerning space and time, namely those of Isaac Newton and Gottfried Wilhelm Leibniz.←51 | 52→
In his famous treatise on light, Opticks (Newton 1730 (in part. Book III, question 31, pp. 350–382) Newton states that physics must abandon the study of qualities, which characterised the old Aristotelian view, focusing instead only on principles which can be empirically