The difference between our sensations and our ideas. We must judge things only by the ideas representing them and never by the sensations by which we are affected in their presence or on their occasion.

THEODORE. Hello, Aristes! How you dream! What are you thinking of so deeply?

ARISTES. Who is it? Ah, Theodore, you surprised me. I am returning from that other world to which you transported me these last days. I am now going there alone, without fearing the phantoms which bar entrance. However, once there I find so many obscure places that I fear being led astray and losing myself.

I. THEODORE. It is a lot, Aristes, to know how to leave one's body when one wishes and to elevate oneself mentally into the land of intellects. But that is not enough. It is necessary to know the map of that land a little, what places are inaccessible to poor mortals, and the places where they can travel freely, without fear of illusions. It seems to me that it is because they have not sufficiently heeded what I am about to draw your attention to that most travelers in these dangerous regions have been seduced by certain attractive specters which entice us to precipices from which return is morally impossible. Listen to me very seriously; today I am going to tell you something you should never forget.