165. The ideas of space, number, and time are common to all men; the proof that they are identical to all is, that, in their application, all are led to the same results, and in speaking of them they all use the same expressions. All men measure space, and its various dimensions; they all count, they all conceive time: why, then, is there so great difficulty in explaining these ideas? why such difference of opinion among philosophers? Here we have a confirmation of what we have said[35] of the strength of direct perception, and the weakness of reflex. When we content ourselves with the direct perception of space, of number, and of time, our ideas are clear, and the understanding feels its strength and energy, it extends the sphere of its knowledge beyond all limits, and raises the edifice of the mathematical and exact sciences. But as soon as it turns upon itself, and, leaving the direct perception, passes to the reflex, endeavoring to perceive its perception, its strength fails, and it falls into a confusion which gives rise to interminable disputes. We scarce perceive that idea, which, a moment ago, we applied to every thing, which penetrated all our cognitions, and circulated, like our life, through all our perceptions; but in its isolation, and its purity, it continually escapes from us; mingled with all things, we see that it is something distinct from them; we separate it from one, and it unites with another; we make an effort to cut it off from all that is not itself, and the mind feels a kind of dizziness come over it, every thing vanishes from before it, and, unable to reach the reality, it is forced to be contented with names, which it pronounces and repeats a thousand times, turning over in them the little reality which they contain. [35] See Bk. I., Chap. III. 167. One of the causes of this weakness and of the errors which are its ordinary consequence, is, as I have before said, our mad desire of representing every idea as an internal form, or image, whereas we ought to consider that in many cases there is only a perception, a simple act in the lowest depth of our mind,--an act, which can be represented by nothing, which resembles nothing, and which cannot be explained in words, because it cannot be decomposed, and it is only present as a simple fact of consciousness. But this fact of consciousness is an active fact; by it we penetrate into things, and see what they have in common, and separate it from what is particular, establishing in our mind, as it were, a central, culminating point, from which we contemplate the internal and the external world, and roam through the boundless regions of possibility. BOOK EIGHTH. THE INFINITE. CHAPTER I. TRANSITORY VIEW OF THE ACTUAL STATE OF PHILOSOPHY.