Humans are just the sort of organisms that interpret and modify their agency through their conception of themselves. This is a complicated biological fact about us.
“To be a character” is to maintain a few qualities, nourish them to excess until they dominate and dictate all others. A character is delineated and thus generally delimited. To “have character” is to have reliable qualities, to hold tightly to them through the temptations to swerve and change. A person of character is neither bribed nor corrupted; he stands fast, is steadfast.
Because characters are public persons, even their private lives can have universal form, general significance. The dramatic character, writ large, can represent for everyman what only later came to be thought of as the inner life of some; it can portray the myth, the conflicts, reversals and discoveries of each person, each polis.