We learn more when we are compelled to invent.

The more we try to improve our schools, the heavier the teaching task becomes; and the better our teaching methods the more difficult they are to apply.

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

What we see changes what we know. What we know changes what we see.

It was while teaching philosophy that I saw how easily one can say ... what one wants to say. ... In fact, I became particularly aware if the dangers of speculation ... It's so much easier than digging out the facts. You sit in your office and build a system. But with my training in biology, I felt this kind of undertaking precarious.

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

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.