The Greek word exousia (ἐξουσία) is one that develops in curious ways.

• In Plato its connotations are often (though not invariably) pejorative: for instance, in the famous story of the Ring of Gyges (Republic, Book II), the trait that Gyges exhibits in using the power of his ring so lavishly is exousia. It is a kind of license, a recklessness in exercising one’s own will without restraint.
• The Stoics, though, gave the word a positive spin. The great goal of the Stoic sage was freedom (eleutheria), and they actually defined freedom as a kind of exousia: “the authority of self-action” (exousia autopragias).
• In the New Testament the word has overwhelmingly positive connotations, and I am especially interested in its use to describe Jesus: “He spoke as one with authority” (ēn gar didaskōn autous hōs exousian echōn) — unlike the scribes and Pharisees. They have the institutional power, but he, this peripatetic sage and prophet, has the real authority. Also, the word often suggests speaking or acting in a way properly “authorized”: See Matthew 8:9 and especially Matthew 28:18: “All authority in heaven and on earth has been given to me” (Edothē moi pasa exousia en ouranō kai epi tēs gēs).

The more I think about this the more I see consistency rather than change in this history. Always, what exousia is depends on the character of the person exercising it. (A distinction we capture in English when we say authoritative or authoritarian.) Exousia in a selfish man, like Gyges, will produce vice; in a sage will produce freedom; in the Son of God will produce compelling teaching, a call to righteousness and intimacy with God. Exousia for Gyges yields self-gratification, while for the Stoic sage it yields self-fulfillment; but in Jesus it manifests itself in words of life for others.