What children can do with the assistance of others might be in some sense even more indicative of their mental development than what they can do alone

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.

The only 'good' learning is that which is in advance of development.

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.

The child begins to perceive the world not only through his [or her] eyes but also through his [or her] speech

Learning is more than the acquisition of the ability to think; it is the acquisition of many specialized abilities for thinking about a variety of things.