Play is the answer to how anything new comes about.
Logic and mathematics are nothing but specialised linguistic structures.
Reflective abstraction, however, is based not on individual actions but on coordinated actions.
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.
Equilibrium is the profoundest tendency of all human activity.
When you teach a child something you take away forever his chance of discovering it for himself.