There are three kinds of brains. The one understands things unassisted, the other understands things when shown by others, the third understands neither alone nor with the explanations of others.
The line has magnitude in one way, the plane in two ways, and the solid in three ways, and beyond these there is no other magnitude because the three are all.
I made a written report which is still today in existence. I have a photocopy of it, and I am saying that in production this aircraft could perhaps substitute for three propeller- driven aircraft of the best existing type. This was my impression.
All the interests of my reason, speculative as well as practical, combine in the three following questions: 1. What can I know? 2. What ought I to do? 3. What may I hope?