Reflective abstraction, however, is based not on individual actions but on coordinated actions.

Knowing reality means constructing systems of transformations that correspond, more or less adequately, to reality.

True interest appears when the self identifies itself with ideas or objects, when it finds in them a means of expression and they become a necessary form of fuel for its activity.

Intelligence is what you use when you don't know what to do.

I could not think without writing.

Logic and mathematics are nothing but specialised linguistic structures.

This means that no single logic is strong enough to support the total construction of human knowledge.