Some conceive ideas to be a sort of image or copy of the object; but this is true only with respect to the representations of the imagination, that is, the purely corporeal; and even here it is necessary to suppose the external world to be such as the senses present it, which, however, under many aspects, is not true. To be convinced how illusory is the theory founded on the likeness of sensible things, we have only to ask, what the image of a relation is, or, how causality, substance, and being are portrayed. In the perception of these ideas, there is something more profound than any thing apparent in sensible things, something of an entirely different order. Necessity has led us to compare the understanding to an eye which sees, and the idea to an image present; but this is only a comparison; the reality is something more mysterious, more secret, more intimate: there is an ineffable union between the perception and the idea: man cannot explain it, but he experiences it. 137. Our consciousness attests that there is in us unity of being, that the soul is at all times identical with itself, and that it remains constant notwithstanding the variety of ideas and of acts which pass over it, like waves over the surface of a lake. Ideas are a mode of being of the mind: but what is this mode? In what does it consist? Does the production and reproduction of ideas proceed from a distinct cause which continually acts upon our soul, and produces immediately those modes of being which we call representations, or ideas? Or must we admit that there has been given to the mind an activity to produce these representations, subject, however, to the determination of exciting causes? These are questions which, for the present, we shall only indicate.(13) CHAPTER XIV. IMPOSSIBILITY OF FINDING THE FIRST PRINCIPLE IN THE IDEAL ORDER. 138. We shall in vain seek in the region of ideas for that which we could not find in that of facts, for there is no ideal truth, the origin of all other truths. Ideal truth only expresses the necessary relation of ideas, abstracting the existence of the objects to which they relate: hence it follows, first of all, that ideal truths are absolutely incapable of producing the knowledge of reality. No ideal truth can lead to any result in the order of existences, unless there be some fact to which it applies. Otherwise, however fruitful it may be in the order of ideas, it will be absolutely sterile in that of facts. The fact without the ideal truth remains in its isolated individuality, incapable of producing any thing more than cognition of itself: but in return, the ideal truth, apart from the fact, remains purely objective in the logical world, and has no means of descending to that of existences.