In the study of nature, men at first all applied themselves, as if in concert, to the satisfaction of the most pressing needs; but when they arrived at knowledge less absolutely necessary, they had to divide it up and each advanced in its course more or less at an equal pace. Thus several sciences have been, as it were, contemporaries; but in the historical ordering of the progress of mind, one can embrace them only in succession.

It is not the same in the encyclopedic ordering of our knowledge. This latter consists in collecting forms of knowledge into the smallest space possible, and in placing, as it were, the philosopher above this vast labyrinth in a highly elevated point of view from which he can perceive at once the principal arts and sciences; see with one glance the objects of his speculations, and the operations which he can perform on those objects; distinguish the general branches of human knowledge, the points where they separate or where they unite; and even catch sight of the secret routes which connect them.