as the only colour which they know; they see it and believe it exists in bodies. Reid tells them that C, is really C, an idea, and that it is incorrect to call it a colour. The real colour is c, an unknown quality. Reid's opponents, the philosophers, agree with Reid in identifying C, with C but they say that C is the colour and not c. Here is only a difference in the application of a name. But there are other differ CHAP. III. SECT. VI. of qualities necessary. ences of greater importance. According to Reid, the sensations of which we Suggestion become aware through the organism necessarily suggest external, and otherwise unknown, qualities, and, by the constitution of our nature, we cannot but believe in the existence of those qualities. To attempt, therefore, either to prove or to disprove their existence is absurd; they are given to us by a law of our nature more fundamental than any process of reasoning we might employ. And any system of philosophy which results in the subversion of this natural and necessary belief must be fallacious either in its original premises or in some of its intermediate processes. Thus to the skepticism of Hume, Reid opposed his doctrine of the necessary suggestion and belief of objective qualities. What is necessarily believed cannot possibly be doubted; the existence of the qualities of bodies is, by a necessity of our nature, believed; therefore, Hume's skepticism is impossible. Such was the reasoning of Reid; and if he could make out the alleged necessity, there can be no question but his reasoning was correct. But, SECT. VI. CHAP. III. unfortunately for his position, both Berkeley and Hume found it possible to doubt that which Reid pronounced to be necessary, and the possibility of an honest doubt is a clear disproof of an alleged necessity. Extension not derived from sen sation. Another doctrine of Reid's, which he himself thought to be of great importance, was directed against one of the premises of idealism. Since the time of Locke it was an accepted maxim amongst English psychologists that all our ideas originate in sense. Upon the principle that there can be no idea which is not the copy of a sensation, Hume founded his skeptical conclusions. And Reid, therefore, saw the importance of endeavouring to show the falsity of this principle. He took the idea of extension as an experimentum crucis; showed that none of our sensations can be extended, while at the same time it cannot be denied that we have a knowledge of extension; and then triumphantly asked where this knowledge could come from. Since it could not possibly come through sense, no sensation being extended, the idealists, Reid thought, must find it utterly impossible to explain its origin upon their principles-while he himself had his instinctive beliefs to fall back upon. Extension is suggested, necessarily and inexplicably, by non-extended sensations, and it has an objective existence as a primary and essential quality of bodies. These two points, the necessity of believing in the existence of objective qualities, and the origin of our knowledge of extension or space, are thought by SECT. VII. Reid to be the most important parts of his philoso- CHAP. III. phy. But perhaps if he and his opponents, the idealists, had understood one another better, there would not have appeared to be such great differences between them. We must now see how the skepticism of Hume was met by a German thinker far more profound than Reid-Immanuel Kant. SECTION VII. KANT (1724-1804). Kritik. § 75. It was the negative skepticism of Hume Kant's which stimulated Kant to produce his great work, the 'Kritik of the pure Reason.' He saw, as Reid also did, that Locke's principle regarding the origin of knowledge naturally led to Hume's conclusion. If all our ideas are simply modified sensations, if all our knowledge arises out of experience, many of our most cherished and valuable beliefs must be undermined. Hence, Kant set himself to show that, although "all our knowledge begins with experience,” yet "it by no means follows that all arises out of our experience.' There are certain elements of our knowledge which could not be derived from experience. "Experience, no doubt, teaches us that this or that object is constituted in such and such a manner, but not that it could not possibly exist otherwise. Now, if we have a proposition which contains the idea of necessity in its very conception, it is a judgment à priori; if, moreover, it is not derived Origin of knowledge. CHAP. III. from any other proposition, unless from one equally involving the idea of necessity, it is absolutely à priori. An empirical judgment never exhibits strict and absolute, but only assumed and comparative, universality." To show that there are such necessary and universal judgments, Kant appeals to the sciences of Mathematics and Physics. We are not concerned with the general use which he makes of this distinction between the à priori and the empirical elements of knowledge; we have only to study its application to the psychology of perception. And in this we shall see a very important difference between the German and the Scottish opponent of Hume. § 76. According to Kant, sensation is the result of objects affecting our sensibility or sensive faculties Sensation. in a particular way. Thus, by means of sensation we have an intuition of phænomenal objects. That in the phænomenon which corresponds to the sensation, Kant calls its matter; but that which effects that the content of the phænomenon can be arranged Matter and under certain relations, he calls its form. But that in which our sensations are merely arranged, and by which they are susceptible of assuming a certain form, cannot be itself sensation. It is, then, the matter of all phænomena that is given to us à posteriori, the form must be ready à priori for them in the mind. By an easy analysis, Kant reaches the conclusion, that the two forms of intuition, without which the cognition of phænomena would be impossible, are Form. *Kant's Introduction. SECT. VII. space and time. It is with the former that we are CHAP. III. now concerned. The following are the principal elements of Kant's exposition of space: (1.) "Space is not a conception which has been Space. derived from outward experiences. For in order that certain sensations may relate to something without me, and in order that I may represent them, not merely as without of, and near to, each other, but also in separate places, the representation of space must already exist as a foundation. (2.) "Space, then, is a necessary representation à priori, which serves for the foundation of all external intuitions. (3.) "Space is no discursive, or as we say, general conception of the relations of things, but a pure intuition. (4.) "Space does not represent any property of objects as things-in-themselves, nor does it represent them in their relations to each other. (5.) "Space is nothing else than the form of all phænomena of the external sense-that is, the subjective condition of the sensibility under which alone external intuition is possible." The substance of Kant's doctrine of perception is Summary of Kant's summed up by himself as follows:doctrine. "All our intuition is nothing but the representation of phænomena; the things which we intuite are not in themselves the same as our representations of them in intuition, nor are their relations in themselves so constituted as they appear to us; and if we take away the subject, or even only the subjective |