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

Scientific knowledge is in perpetual evolution; it finds itself changed from one day to the next.

Punishment renders autonomy of conscience impossible.

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.

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.

Moral autonomy appears when the mind regards as necessary an ideal that is independent of all external pressures.

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.