The specifically human capacity for language enables children to provide for auxiliary tools in the solution of difficult tasks, to overcome impulsive action, to plan a solution to a problem prior to its execution, and to master their own behavior.

Psychology teaches us at every step that though two types of activity can have the same external manifestation, whether in origin or essence, their nature may differ most profoundly.

There is reason to believe that voluntary activity, more than highly developed intellect, distinguishes humans from the animals which stand closest to them.

A word devoid of thought is a dead thing, and a thought unembodied in words remains a shadow.

Every function in the child's cultural development appears twice: first, on the social level, and later, on the individual level; first, between people (interpsychological) and then inside the child (intrapsychological). This applies equally to voluntary attention, to logical memory, and to the formation of concepts. All the higher functions originate as actual relationships between individuals.

In play, the child is always behaving beyond his age, above his usual everyday behaviour; in play he is, as it were, a head above himself. Play contains in a concentrated form, as in the focus of a magnifying glass, all developmental tendencies; it is as if the child tries to jump above his usual level.

What a child can do today with assistance, she will be able to do by herself tomorrow.