"The development of the child is a complex dialectical process characterized by periodicity, unevenness in the development of different functions, metamorphosis or qualitative transformation of one form into another, intertwining of external and internal factors, and adaptive processes overcoming impediments that the child encounters."
"The only good learning is that which is in advance of development."
"Play is not the predominant form of activity in children, but it is a very important form and may well be, at a certain period, the leading activity in which the future motives that will govern the child's actual, serious life and activity in the future are developed."
"Learning awakens a variety of internal developmental processes that are able to operate only when the child is interacting with people in his environment and in cooperation with his peers."
"A child's learning begins long before he attends school."