![]() | CHAPTER I. Of the Principles of Pure Practical Reason. Kant`s Critique of Practical Reason and Other Works on The Theory of Ethics | ![]() |
II. Of the Right that Pure Reason in its Practical use has to an Extension which is not possible to it in its Speculative Use.
We have in the moral principle set forth a law of causality, the determining principle of which is set above all the conditions of the sensible world; we have it conceived how the will, as belonging to the intelligible world, is determinable, and therefore we therefore we have its subject (man) not merely conceived as belonging to a world of pure understanding, and in this respect unknown (which the critique of speculative reason enabled us to do), but also defined as regards his causality by means of a law which cannot be reduced to any physical law of the sensible world; and therefore our knowledge is extended beyond the limits of that world, a pretension which the Critique of Pure Reason declared to be futile in all speculation. Now, how is the practical use of pure reason here to be reconciled with the theoretical, as to the determination of the limits of its faculty?
David Hume, of whom we may say that he commenced the assault on the claims of pure reason, which made a thorough investigation of it necessary, argued thus: The notion of cause is a notion that involves the necessity of the connexion of the existence of different things (and that, in so far as they are different), so that, given A, I know that something quite distinct there from, namely B, must necessarily also exist.
Mathematics escaped well, so far, because Hume thought that its propositions were analytical; that is, proceeded from one property to another, by virtue of identity and, consequently, according to the principle of contradiction. This, however, is not the case, since, on the contrary, they are synthetical; and although geometry, for example, has not to do with the existence of things, but only with their a priori properties in a possible intuition, yet it proceeds just as in the case of the causal notion, from one property (A) to another wholly distinct (B), as necessarily connected with the former. Nevertheless, mathematical science, so highly vaunted for its apodeictic certainty, must at last fall under this empiricism for the same reason for which Hume put custom in the place of objective necessity in the notion of cause and, in spite of all its pride, must consent to lower its bold pretension of claiming assent a priori and depend for assent to the universality of its propositions on the kindness of observers, who, when called as witnesses, would surely not hesitate to admit that what the geometer propounds as a theorem they have always perceived to be the fact, and, consequently, although it be not necessarily true, yet they would permit us to expect it to be true in the future. In this manner Hume's empiricism leads inevitably to scepticism, even with regard to mathematics, and consequently in every scientific theoretical use of reason (for this belongs either to philosophy or mathematics). Whether with such a terrible overthrow of the chief branches of knowledge, common reason will escape better, and will not rather become irrecoverably involved in this destruction of all knowledge, so that from the same principles a universal scepticism should follow (affecting, indeed, only the learned), this I will leave everyone to judge for himself.
As regards my own labours in the critical examination of pure reason, which were occasioned by Hume's sceptical teaching, but went much further and embraced the whole field of pure theoretical reason in its synthetic use and, consequently, the field of what is called metaphysics in general; I proceeded in the following manner with respect to the doubts raised by
It resulted, however, from my inquiries, that the objects with which we have to do in experience are by no means things in themselves, but merely phenomena; and that although in the case of things in themselves it is impossible to see how, if A is supposed, it should be contradictory that B, which is quite different from A, should not also be supposed (i.e., to see the necessity of the connection between A as cause and B as effect); yet it can very well be conceived that, as phenomena, they may be necessarily connected in one experience in a certain way (e.g., with regard to time-relations); so that they could not be separated without contradicting that connection, by means of which this experience is possible in which they are objects and in which alone they are cognisable by us. And so it was found to be in fact; so that I was able not only to prove the objective reality of the concept of cause in regard to objects of experience, but also to deduce it as an a priori concept by reason of the necessity of the connection it implied; that is, to show the possibility of its origin from pure understanding without any empirical sources; and thus, after removing the source of empiricism, I was able also to overthrow the inevitable consequence of this, namely, scepticism, first with regard to physical science, and then with regard to mathematics (in which empiricism has just the same grounds), both
But how is it with the application of this category of causality (and all the others; for without them there can be no knowledge of anything existing) to things which are not objects of possible experience, but lie beyond its bounds? For I was able to deduce the objective reality of these concepts only with regard to objects of possible experience. But even this very fact, that I have saved them, only in case I have proved that objects may by means of them be thought, though not determined a priori; this it is that gives them a place in the pure understanding, by which they are referred to objects in general (sensible or not sensible). If anything is still wanting, it is that which is the condition of the application of these categories, and especially that of causality, to objects, namely, intuition; for where this is not given, the application with a view to theoretic knowledge of the object, as a noumenon, is impossible and, therefore, if anyone ventures on it, is (as in the Critique of Pure Reason) absolutely forbidden. Still, the objective reality of the concept (of causality) remains, and it can be used even of noumena, but without our being able in the least to define the concept theoretically so as to produce knowledge. For that this concept, even in reference to an object, contains nothing impossible, was shown by this, that, even while applied to objects of sense, its seat was certainly fixed in the pure understanding; and although, when referred to things in themselves (which cannot be objects of experience), it is not capable of being determined so as to represent a definite object for the purpose of theoretic knowledge; yet for any other purpose (for instance, a practical) it might be capable of being determined so as to have such application. This could not be the case if, as Hume maintained, this concept of causality contained something absolutely impossible to be thought.
In order now to discover this condition of the application of the said concept to noumena, we need only recall why we are not content with its application to objects of experience, but
But, besides the relation in which the understanding stands to objects (in theoretical knowledge), it has also a relation to the faculty of desire, which is therefore called the will, and the pure will, inasmuch as pure understanding (in this case called reason) is practical through the mere conception of a law. The objective reality of a pure will, or, what is the same thing, of a pure practical reason, is given in the moral law a priori, as it were, by a fact, for so we may name a determination of the will which is inevitable, although it does not rest on empirical principles. Now, in the notion of a will the notion of causality is already contained, and hence the notion of a pure will contains that of a causality accompanied with freedom, that is, one which is not determinable by physical laws, and consequently is not capable of any empirical intuition in proof of its reality, but, nevertheless, completely justifies its objective reality a priori in the pure practical law; not, indeed (as is easily seen) for the purposes of the theoretical, but of the practical use of reason. Now the notion of a being that has free will is the notion of a causa noumenon, and that this notion involves no contradiction, we are already assured by the fact- that inasmuch as the concept of cause has arisen wholly from pure understanding, and has its objective reality assured by the deduction, as it is moreover in its origin independent of any sensible conditions, it is, therefore, not restricted to phenomena (unless we wanted
If, with Hume, I had denied to the notion of causality all objective reality in its [theoretic] use, not merely with regard to things in themselves (the supersensible), but also with regard to the objects of the senses, it would have lost all significance, and being a theoretically impossible notion would have been declared to be quite useless; and since what is nothing cannot be made any use of, the practical use of a concept theoretically null would have been absurd. But, as it is, the concept of a causality free from empirical conditions, although empty, i.e., without any appropriate intuition), is yet theoretically possible, and refers to an indeterminate object; but in compensation significance is given to it in the moral law and consequently in a practical sense. I have, indeed, no intuition which should determine its objective theoretic reality, but not the less it has a real application, which is exhibited in concreto in intentions or maxims; that is, it has a practical reality which can be specified, and this is sufficient to justify it even with a view to noumena.
Now, this objective reality of a pure concept of the understanding in the sphere of the supersensible, once brought in,
![]() | CHAPTER I. Of the Principles of Pure Practical Reason. Kant`s Critique of Practical Reason and Other Works on The Theory of Ethics | ![]() |