The self thus becomes aware of itself, at least in its practical action, and discovers itself as a cause among other causes and as an object subject to the same laws as other objects.

Logic and mathematics are nothing but specialised linguistic structures.

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

Play is the answer to how anything new comes about.

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

Play is the work of childhood.

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