We learn more when we are compelled to invent.

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.

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

Equilibrium is the profoundest tendency of all human activity.

Every acquisition of accommodation becomes material for assimilation, but assimilation always resists new accommodations.

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

In genetic epistemology, as in developmental psychology, too, there is never an absolute beginning.