It is desire that engenders belief and if we fail as a rule to take this into account, it is because most of the desires that create beliefs end only with our own life.

A little insomnia is not without its value in making us appreciate sleep, in throwing a ray of light upon that darkness.

Even the simple act that we call "going to visit a person of our acquaintance" is in part an intellectual act. We fill the physical appearance of the person we see with all the notions we have about him, and in the totality of our impressions about him, these notions play the most important role.

Medicine being a compendium of the successive and contradictory mistakes of medical practitioners, when we summon the wisest of them to our aid, the chances are that we may be relying on a scientific truth the error of which will be recognized in a few years time.

For although we know that the years pass, that youth gives way to old age, that fortunes and thrones crumble (even the most solid among them) and that fame is transitory, the manner in which—by means of a sort of snapshot—we take cognisance of this moving universe whirled along by Time, has the contrary effect of immobilising it.

Each reader reads only what is already within himself. The book is only a sort of optical instrument which the writer offers to the reader to enable the latter to discover in himself what he would not have found but for the aid of the book.

We can only be faithful to what we remember, and we remember only what we have known.