&c.--But it is especially in Science that the use of conceptions is important; for they are, properly speaking, its materials. The aims of all the sciences may, indeed, in the last resort, be reduced to knowledge of the particular through the general; now this is only possible by means of the _dictum de omni et nullo_, and this, again, is only possible through the existence of conceptions. Aristotle therefore says: ἄνευ μὲν γὰρ τῶν καθόλου οὐκ ἔστιν ἐπιστήμην λαβεῖν[119] (_absque universalibus enim non datur scientia_). Conceptions are precisely those _universalia_, whose mode of existence formed the argument of the long controversy between the Realists and Nominalists in the Middle Ages. [119] Aristot. "Metaph." xii. c. 9, "For without universals it is impossible to have knowledge." (Tr.'s Add.) § 28. _Representatives of Conceptions. The Faculty of Judgment._ Conceptions must not be confounded with pictures of the imagination, these being intuitive and complete, therefore individual representations, although they are not called forth by sensuous impressions and do not therefore belong to the complex of experience. Even when used to _represent a conception_, a picture of the imagination (phantasm) ought to be distinguished from a conception. We use phantasms as _representatives of conceptions_ when we try to grasp the intuitive representation itself that has given rise to the conception and to make it tally with that conception, which is in all cases impossible; for there is no representation, for instance, of dog in general, colour in general, triangle in general, number in general, nor is there any picture of the imagination which corresponds to these conceptions. Then we evoke the phantasm of some dog or other, which, as a representation, must in all cases be determined: that is, it must have a certain size, shape, colour, &c. &c.; even though the conception represented by it has no such determinations. When we use such _representatives of conceptions_ however, we are always conscious that they are not adequate to the conceptions they represent, and that they are full of arbitrary determinations. Towards the end of the first part of his Twelfth Essay on Human Understanding, Hume expresses himself in agreement with this view, as also Rousseau in his "Discours sur l'Origine de l'Inégalité."[120] Kant's doctrine, on the contrary, is a totally different one. The matter is one which introspection and clear reflection can alone decide. Each of us must therefore examine himself as to whether he is conscious in his own conceptions of a "Monogram of Pure Imagination _à priori_;" whether, for instance, when he thinks dog, he is conscious of something _entre chien et loup_; or whether, as I have here explained it, he is either thinking an abstract conception through his Reason, or representing some representative of that conception as a complete picture through his imagination. [120] Part the First, in the middle.