The basic strength called purpose should be realized during the muscular-anal stage,which is characterized by Autonomy versus Doubt and Shame.

Muscular-anal Stage

In psychoanalytic theory, a developmental phase focusing on toilet training where children learn to exert control over bodily functions.

Autonomy versus Doubt

A psychological conflict of early childhood, as theorized by Erik Erikson, where children must develop a sense of personal control and independence, or they may experience shame and doubt in their abilities.