123. Still we must confess that Kant, in the second edition of his _Critic of Pure Reason_, rejects these conclusions, and expressly combats idealism. There is no necessity of examining how far the second edition contradicts the first: it is sufficient for me to inform the reader that this contradiction exists, and that in the first edition there are expressions which so plainly lead to idealism, that it is impossible not to be surprised on finding the same author in the second edition of his work strongly opposing the idealist system. I have pointed out the consequences of the doctrine; if the author understood it in a different sense from that which his words expressed, this is merely a personal, not a philosophical question.(31) CHAPTER XVIII. THE PROBLEM OF SENSIBLE EXPERIENCE. 124. The great problem of philosophy does not consist in the explanation of the possibility of experience; but in establishing the reason of the consciousness of experience, as experience. Experience in itself is a fact of our soul attested by consciousness, but _to know_ that this fact is a fact of experience, is something very different from mere experience; for, by knowing this, we pass from the subjective to the objective, referring to the external world what we experience within us. We refer objects to different points of space, and regard them as outside of, and distinct from, each other: to say that the instinct by which we so regard them is a condition of the subject and of sensible experience is to establish a sterile fact. The difficulty is in knowing why we have this instinct; why the representation of an extension is in our soul; and why this subjective extension in a simple being should be presented to our perception as the image of something external and really extended. 125. Transcendental esthetics may determine the following problems: I. To explain what is the subjective representation of extension, abstracted from all that is objective. II. Why this representation is found in our soul. III. Why a simple being contains in itself the representation of multiplicity, and an unextended being the representation of extension. IV. Why and how we pass from ideal to real extension. V. To determine how far we may apply to extension what is true of the other sensations, which are considered as phenomena of our soul, having no external object like them, and no other correspondence with the external world than the relation of effects to their cause. 126. What is the subjective representation of extension, abstracted from all that is objective? It is a fact of our soul; no further explanation is possible; he that has it, knows what it is; he that has it not, does not, except intelligences of a higher order, which know what this representation is, without experiencing it as we do.