The use of the senses in the sciences. In our sensations there is a clear idea and confused sensations. The idea does not belong to the sensation. It is the idea which enlightens the mind, and the sensation which preoccupies it and makes it attentive, for it is by means of the sensation that the intelligible idea becomes sensible.

ARISTES. I have made great headway, Theodore, since you left me. I have indeed discovered land. I have generally reviewed all the objects of my senses, having been led, it seems to me, solely by Reason. Though already somewhat accustomed to these new discoveries, never was I more surprised. Good God, what poverty I discerned in what two days ago appeared to me to be perfect magnificence! What wisdom, what greatness, what wonders in everything the world scorns! People who see only with their eyes are surely strangers in their own land. They admire everything and know nothing, too happy if what strikes them does not kill them. There are perpetual illusions on the part of sensible objects. Everything deceives us, poisons us, speaks to the soul only for the body. Only Reason disguises nothing. How pleased I am with it and with you for having taught me to consult it, for having elevated me above my senses and myself in order to contemplate the light! I have recognized very clearly, it seems to me, the truth of everything you have told me.