Piaget believed that children made moral judgments based on their own observations of the world.

Piaget's theory of morality was radical when his book The Moral Judgment of the Child was published in 1932 for two reasons: his use of philosophical criteria to define morality (as universalizable, generalizable, and obligatory) and his rejection of equating cultural norms with moral norms. Piaget, drawing on Kantian theory, proposed that morality developed out of peer interaction and that it was autonomous from authority mandates. Peers, not parents, were a key source of moral concepts such as equality, reciprocity, and justice.