In play, 

a child is always above his average age, 

above his daily behaviour; 

in play, 

it is as though he were 

a head taller than himself.

The most significant moment in the course of intellectual development, 

which gives birth to the purely human forms of practical and abstract intelligence, 

occurs when speech and practical activity, 

two previously completely independent lines of development, 

converge.

A mind cannot be independent of culture.