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.

Each time one prematurely teaches a child something he could have discovered himself, that child is kept from inventing it and consequently from understanding it completely.

During the earliest stages the child perceives things like a solipsist who is unaware of himself as subject and is familiar only with his own actions.

Logical positivists have never taken psychology into account in their epistemology, but they affirm that logical beings and mathematical beings are nothing but linguistic structures.

The current state of knowledge is a moment in history, changing just as rapidly as the state of knowledge in the past has ever changed and, in many instances, more rapidly.

What is desired is that the teacher ceased being a lecturer, satisfied with transmitting ready-made solutions. His role should rather be that of a mentor stimulating initiative and research.

Equilibrium is the profoundest tendency of all human activity.