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.

What the genetic epistemology proposes is discovering the roots of the different varieties of knowledge, since its elementary forms, following to the next levels, including also the scientific knowledge.

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

Every time we teach a child something, we keep him from inventing it himself. On the other hand, that which we allow him to discover for himself will remain with him visible for the rest of his life.

Logic and mathematics are nothing but specialised linguistic structures.

I could not think without writing.

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.