Teaching means creating situations where structures can be discovered.
Play is the answer to how anything new comes about.
To express the same idea in still another way, I think that human knowledge is essentially active.
Play is the work of childhood.
It is with children that we have the best chance of studying the development of logical knowledge, mathematical knowledge, physical knowledge, and so forth.
Knowing reality means constructing systems of transformations that correspond, more or less adequately, to reality.