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Fr. Seamus Mulholland

The Critical Philosophy of Immanuel Kant

Kant's Contribution to Philosophy: The meaning of 'Critique'

Criticism is Kant's original achievement; it identifies him as one of the greatest thinkers of mankind and as one of the most influential authors in contemporary philosophy. But it is important to understand what Kant means by'criticism', or 'critique'. In a general sense the term refers to a general cultivation of reason 'by way of the secure path of science' (Bxxx). More particularly, its use is not negative, but positive, a fact that finds expression in the famous expression, 'I have therefore found it necessary to deny knowledge to make room for faith' (Bxxx). Correspondingly, its negative use consists in not allowing one's self to 'venture with speculative reason beyond the limits of experience' (Bxxiv). Thus, criticism removes the decisive hindrance that threatens to supplant or even destroy the 'absolutely necessary practical employment of pure which it {pure reason} inevitably goes beyond the limits of sensibility' (Bxxv). Accordingly, the critique guarantees a secure path for science by confining speculative reason and by giving practical reason the complete use of its rights: rights that thus far had not been recognised.

Place in the History of Ideas

Kant, being confronted with the two extremes of rationalism and empiricism, set for himself the task of creating a synthesis of the two. As he saw it, rationalism operates in the sphere of innate ideas, with their analytical and therefore aprioristic ideas; this necessity, however, is not based on experience and consequently does not apply to reality itself. On the other hand empiricism starts completely from experience and thus (it seems) from reality, but it arrives only at a posteriori and therefore synthetic statements that lack necessity. Kant sought to unite the concept and experience; he sought a necessity that extends to the order of objective reality and an order of objective reality that in itself contains necessity. This interpenetration finds its expression in judgements that are a priori and yet synthetic, on the one hand, and yet synthetic and a priori on the other. Kant thought that he could attain this goal only by way of a 'changed point of view' (Bxvi) referred to as a 'Copernician revolution'. 'On the supposition, thus far considered valid, that 'all our knowledge must conform to objects' (Bxvi), a priori judgements that enlarge Man's knowledge synthetically are impossible. Here, one needs the opposite assumption, according to which 'we suppose that objects must conform to our knowledge' (Bxvi); only in this way we are able to 'have knowledge of objects a priori determining something in regard to them prior to their being given' (ibid.) Consequently, 'we can know a priori of things only what we ourselves put into them' (Bxviii); this means that the process of knowing a priori 'has to do only with appearances, and must leave the thing-in-itself as indeed real per se, but as not known by us' (Bxx). Since, however, all of metaphysics aims at the thing-in-itself, speculative reason, by which, as had been said, we 'never transcend the limits of possible experience' (Bxix), is unable to rise to the metaphysical level.

Kant's Critique of Knowledge

Kant perfects his criticism of knowledge in the Critique of Pure Reason, which moves from transcendental aesthetics to transcendental logic; and, within the latter, from transcendental analytics to transcendental dialectics. Throughout, the investigation revolves around the synthetic a priori judgements that have been mentioned above; these are synthetic insofar as they extend knowledge through a predicate that is not contained in the concept of the subject;, they are a priori insofar as they have a necessary and universal validity, and this previous to any actual experience of individual cases. All of this, however, leads to the question, 'How are a prior synthetic judgements possible?' (B19). To put it more accurately, these judgements are questioned as to the condition for their possibility; such conditions, on the terms of the Copernician revolution, can be found only in the subject. Kant here develops his transcendental method, a method by which he transcends a priori knowledge and arrives at the level of the conditions for possibility, which are already marked out in the subject.

Mathematics and natural sciences, for him, have already followed the certain path of science. Thus, as he points out in detail, they contain a number of synthetic a priori judgements that are valid without further discussion. Consequently, one has to prove not that they are valid, but how their accepted validity is possible. To explain this, Kant gores back to the distinction between matter and form in human knowledge. The matter coincides with sensation, 'this is the effect of an object on the faculty of representation, so far as we are affected by it' (A19); only in this way 'can the object be given to us' (A19). Matter, taken a posteriori as unordered multiplicity, has as its opposite complement form, 'in which alone sensation can be posited' and connected 'in certain relationships' (A20); this form 'must lie ready for the sensations a priori in the mind' (A20). At this point one must explain the three domains of a priori forms.

First, is the region of sense knowledge. This is the field of receptivity by which 'we are affected by the objects' (A19); 'objects given to us by means of sensibility, and it alone yields us intuitions' (ibid). Now, that intuition is called empirical 'which is in relation to the object through sensation' (A20) and which is therefore based on received impressions. By way of contrast, a pure intuition is that 'in which there is nothing that belongs to sensation' (ibid.) 'it belongs to pure form of sensibility' (ibid.) and is actuated in the mind a priori, even without a given object. Correspondingly transcendental aesthetics is 'the science of all principles of a priori sensibility' (A21); but these are two 'namely, space and time' (A22), and they are the conditions for the possibility of the a priori synthetic judgements of mathematics. Space is more particularly the form of the external sense faculties i.e. 'the subjective condition of sensibility, under which alone outer intuition is possible for us' (A26). Time on the other hand, is 'the form of inner sense, that is, of the intuition of ourselves and of our inner state' (A33). Again, time 'is the formal a priori condition of all appearances whatsoever' (A34) because the external representations also belong 'in themselves , as determinations of the mind, to our inner state' (A34). To space and time is ascribed 'empirical reality' (A35), that is, an objective validity, as the conditions alone that enable Man to perceive objects; in the same way they have a 'transcendental ideality' (A36) in so far as they are merely conditions of our sensibility and cannot in any way, be ascribed to 'things as they are in themselves' (A39). Thus, it is true they make a priori synthetic suppositions possible, but these apply to objects 'only insofar as objects are viewed as appearances, and do not represent things are they are in themselves' (A39).

Second, is the area of reason. As spontaneity in the production concepts, reason co-operates with the sense faculties, which are 'receptivity for impressions' (A50); through these impressions the object is 'given' whereas through reason it is 'thought' (A50). Knowledge can arise 'through their union' for thoughts with concepts are blind and intuitions with concepts are empty. Everything depends on the pure concepts; in these, 'there is no mingling of sensation' (A51). Thus transcendental analytics consists in the dissection of the faculty of understanding itself insofar as, in this faculty the pure concepts have been located and prepared in an a priori way. (A65-66). It is thus that the synthetic a priori judgements of natural science are explained with regard to their possibility. Hence the question is how to seek pure concepts on the basis of a single principle and how to determine in an a priori manner their systematic completeness. (A67). Because reason reaches only to the mediate knowledge of an object, or judgements, it constitutes a 'a faculty of judgement' (A 69). The elementary forms of judgement are outlined in it; from the point of view of the mere form of understanding they can be classified 'under four heads, each of which contains three moments' (A70). Coordinated in these are the 12 pure concepts of understanding (e.g. substance, causality etc.) which apply 'a priori to objects of intuition in general ' (A79) as the true primary concepts of the pure understanding they are called 'the categories' (A80).

To the process of educing them is linked transcendental deduction, which shows that the categories are 'conditions of the possibility of experience and are therefore valid a priori for all objects of experience' (B161). However, objects must be understood not as things in themselves, but as appearances in space and time that are determined by the categories (B168-169). Consequently there can be no a priori knowledge, except of objects of possible experience (B166). Subject to the same limitations are the principles that teach reason (being for potency for judging) how, 'to apply to appearances the concepts of understanding' (A132). To these principle belongs the principle of succession in time in accordance with the law of causality: all alterations take place in the conformity with the law of the connection of cause and effect (A189, B232)

Third, is the study of the intellect, which is the concern of transcendental dialectics. Here the synthetic a priori judgements of metaphysics are examined as to their possibility. The question is not how they are possible, but simply whether they are possible. Kant's answer is that they are not. Here his concern is to show the 'transcendental illusion' (A297); it is a natural and inevitable illusion (A298), and thus it has been able to lead metaphysics astray until now. The critique must be applied to 'transcendental principles' that in contrast to immanent principles, lead Man to go beyond the limits of possible experience (A295). At the basis of these principles one finds 'transcendental ideas' designed by reason in an a priori and necessary fashion:

'No object adequate to the transcendental idea can ever be found within experience..for they view all knowledge gained in experience as being determined by an absolute totality of an absolute whole.' (A327)

From the different ways of drawing conclusions, Kant gathers that there are three and only three ideas, namely:

  1. The soul as the absolute unconditioned unity of the thinking subject
  2. The world as the absolute unity of a series of conditions of appearance
  3. God as the absolute unity of the condition of all objects of thought in general (A334)

These ideas never allow of any constitutive employment as supplying certain objects. In other words, the objects that are outlined in these ideas are never recognised through them; for ideas that go as far as the thing-in-itself remain empty, because the intellectual intuition that complements them and reaches out into the realm of the thing in itself has not been given to man. On the other hand these ideas have an indispensably necessary, regulative employment insofar as they put before the intellect 'the form of a whole of knowledge' and in this way can determine a priori for every part of its position and relative to other parts (A644-645). This delimitation of their use is opposed by the sophistications that rise from the very nature of reason and claim to form a bridge from ideas to their corresponding objects. The four paralogisms intend to proceed from the transcendental concept of the subject to a science concerning the nature of thinking being. Just as rational psychology is impossible, so also is rational cosmology (A340, 345, 408). When the latter is attempted as the absolute totality of condition for any given appearance. In like fashion there can be no rational theology (A631) for all three kinds of proof for the existence of God are inconclusive, since the physico-theological proof rests upon the cosmological proof and the cosmological proof upon the ontological proof (A630), which itself suffers from an illegitimate transition from the realm of concepts to the realm of reality. What is left of God is only the transcendental ideal, as the concept of all reality and the complete determination of things without requiring that this reality be objectively given and itself a thing.

A Critical Appraisal

With the ability of a genius Kant aspired to create a grand synthesis between sense knowledge and intellectual knowledge between Man's theoretical and practical activity. The transcendental method was his way to achieve this. In this undertaking he obtained noteworthy results: the unity of human cognition, its necessity and universality, the significance of the a priori, the absoluteness of the moral imperative, the foundation of existence in the metaphysical order, and the transcendental problematics. And yet Kant's synthesis, taken as a whole, fails. It does so because he remained too much subject to the limitations of his own historical situation and therefore, was not able to go deeply enough and penetrate ultimate depths.

From the point of view of Heidegger one may summarise Kant's failure in his being unaware of 'Being'. How much this is the case is clearly shown in his distinction between intellect and reason. The reason is rightly considered the faculty that, by way of fundamental concepts or categories, permeates sensible phenomena; this is equivalent to the ration of Aquinas and its corresponding quiddity. Kant's intellect on the other hand, reaches out into the metaphysical realm with its three ideas but never manages to conclusively penetrate it. The basis for this restriction lies in the intellect's having lost, for Kant, its proper orientation toward being as all-inclusive, and orientation that allows Man to enter the metaphysical realm in the first place. For Aquinas, intellectus is intrinsically orders to ens, which is grounded in esse. In this connection, Kant considers intellect as completely excluded from any form of intellectual intuition.

The transcendental method can be carried through in a way that goes beyond Kant himself to arrive at being as the primary condition for the possibility of all human knowledge, even of all human action. This basic idea has far reaching consequences. The proof for God's existence is somehow precontained in the orientation of intellect toward being; thus does theoretical metaphysics become possible. Being, too, enables a priori knowledge to reveal rather than conceal, as it must do for Kant. Again the formal objects of the soul's faculties in Aquinas corresponds to Kant's forms; thus knowledge through categories is not restricted to that which is 'for Man' but opens up to that which is 'in itself'. Finally, the absoluteness of Kant's moral imperative also receives its foundation in being, and thus theory and practice are brought into harmony.


Balterson, D. The Philosophy of Immanuel Kant Toronto, 1984

Jewson, M. Kant and the Critique of Pure Reason Rome, 1986

Kant, I. Critique of Pure Reason N.K. Smith tr London, 1929

McConnor, T. The Philosophy of the Enlightenment London, 1989

Tonderson, P. Immanuel Kant: The Critique of Of Pure Reason New York, 1987

Wallis, H. The Thought of Immanuel Kant New York, 1955

O Neill, P., SJ, Kant and Aquinas: A Comparative Study, Rome, 1967