To Kant's mind, the failure of all previous philosophy to construct a permanent system, and the frequent return of scepticism as the prevailing attitude of investigators in that field, was due to what he conceived to be a vain attempt to establish knowledge on the assumption that our ideas of the object should conform to the nature of the object itself. He will proceed, accordingly, on the opposite assumption, viz., that the subject determines the object, that instead of our ideas being conformed to the nature of the object, the object of knowledge is itself determined by the manner in which the mind, by its very nature, receives and works up the materials supplied it. This change of standpoint led Kant to seek for the forms or modes of perception and judgment which guide us in the knowing of objects. And since these forms or modes, as belonging to the nature of the mind, determine the manner in which we perceive and know, it follows as a matter of course, thought Kant, that we can never know things as "they are in themselves," but only the manner in which they appear to us, i.e., their phenomena.The vast "a priori" machinery employed by Kant in his "construction of the object" seems to have so overshadowed in his own mind, as it has in the minds of his students and interpreters since, the question of the contribution of the object itself (the "thing in itself") to that construction that we are given no explicit statements by Kant in the matter; and, to my knowledge, no systematic investigation of the problem has been undertaken by any one of the host of writers, small and great, who have professed to furnish us with expositions of his system. Accordingly it does not seem superfluous to institute an inquiry into "the Epistemological function of the 'thing- in itself in Kant's philosophy," as this essay aims to do. Here we shall not be concerned so much with the question whether Kant believed in the existence of things in themselves as with this other, how much or how little does the so-called 'thing in itself contribute to our knowledge of objects? If it should be found that it contributes nothing at all, that for knowledge it has no function, then it will be time enough to ask, does the 'thing in itself exist for Kant? And if so, how does he arrive at this conclusion?If we adopt the terminology of common sense and call the a priori forms of Sensibility and the categories of the Understanding subjective, we may say that this essay aims to be an enquiry into the objective factors of knowledge, as set forth or implied in the philosophy of Kant. It will have to deal, then, primarily, with such questions as these: -What function has the thing in itself in determining the form of objects in experience and their relations to one another? Is there any characteristic in things which has an influence in the determination of the spatial relations of objects? Or even if the mind bring to objects their general spatial quality, what about the particular space forms? Are these due to the action of the 'thing in itself upon sensibility, otherwise than the general quality of extension is? In the case of the categories, too, must the mind be regarded as the sole agent in their adaptation, or, is the cue for their employment given in sense? And further, as the only means of finding an answer to the above questions, we must decide whether Kant attributed to the 'thing in itself the function of so affecting the senses as to produce sensations within us....