It is self-evident that under these circumstances no other advice can be given as to how one may enter into the thought explained in this work than _to read the book twice_, and the first time with great patience, a patience which is only to be derived from the belief, voluntarily accorded, that the beginning presupposes the end almost as much as the end presupposes the beginning, and that all the earlier parts presuppose the later almost as much as the later presuppose the earlier. I say “almost;” for this is by no means absolutely the case, and I have honestly and conscientiously done all that was possible to give priority to that which stands least in need of explanation from what follows, as indeed generally to everything that can help to make the thought as easy to comprehend and as distinct as possible. This might indeed to a certain extent be achieved if it were not that the reader, as is very natural, thinks, as he reads, not merely of what is actually said, but also of its possible consequences, and thus besides the many contradictions actually given of the opinions of the time, and presumably of the reader, there may be added as many more which are anticipated and imaginary. That, then, which is really only misunderstanding, must take the form of active disapproval, and it is all the more difficult to recognise that it is misunderstanding, because although the laboriously-attained clearness of the explanation and distinctness of the expression never leaves the immediate sense of what is said doubtful, it cannot at the same time express its relations to all that remains to be said. Therefore, as we have said, the first perusal demands patience, founded on confidence that on a second perusal much, or all, will appear in an entirely different light. Further, the earnest endeavour to be more completely and even more easily comprehended in the case of a very difficult subject, must justify occasional repetition. Indeed the structure of the whole, which is organic, not a mere chain, makes it necessary sometimes to touch on the same point twice. Moreover this construction, and the very close connection of all the parts, has not left open to me the division into chapters and paragraphs which I should otherwise have regarded as very important, but has obliged me to rest satisfied with four principal divisions, as it were four aspects of one thought. In each of these four books it is especially important to guard against losing sight, in the details which must necessarily be discussed, of the principal thought to which they belong, and the progress of the whole exposition. I have thus expressed the first, and like those which follow, unavoidable demand upon the reader, who holds the philosopher in small favour just because he himself is a philosopher.