In chapter 2 of his 2010 book, Up with Authority, Victor Lee Austin offers a description of this misunderstood (and largely abandoned) concept.
“In English, the word has an obvious root: ‘author.’ We should understand this authorship as at once active and passive. An authority, who is able to ‘authorize’ the actions of others, is at the same time one whose own actions are authorized. So does etymology place us at once within a world of interconnections. Authorities are not lone rangers or loose cannons; they are not disconnected and unaccountable. To be an authority is to be authorized by someone or something beyond oneself. Thus the centurion who has appealed to Jesus to heal his servant asked Jesus not to come to his house: ‘only speak the word, and my servant will be healed.’ This itself is an expression of faith in Jesus, that he is able to heal at a distance, simply by speaking. But the centurion’s insight goes further:. ‘I also am a man under authority,’ he says, ‘with soldiers under me; and I say to one, “Go,” and he goes, and to another, “Come,” and he comes.’ The centurion has authority because he is under authority. It is striking that he doesn’t say to Jesus, ‘You and I are both authorities in our various realms; I am able to command and others do what I say; you too can command spirits and elements and they do what you say.’ Rather, he says first, ‘I also am a man under authority.’ His faith is that he sees Jesus as ‘a man under authority,’ implicitly, the authority of the father.
“The Greek is exousia. Is it fanciful to see embedded here the word for ‘being,’ ousia, and thus a rooting of authority in our nature? Authority, exousia, is formed from exesti, a verb that exists only in the impersonal third person and has for its earliest meaning ‘it is allowed, it is in one’s power, is possible.’ And exousia in ordinary Greek means the ‘ability to perform an action,’ early extended to a right of action or a right to disposal, particularly as that right was given from above. Nonetheless, we can note that this word that comes to mean power in the sense of authority is compounded from ek and ousia. That etymology gives us ‘out of being’ or ‘from being,’ suggesting for the philosophical mind that human authority comes out of human being, that it is deeply in accord with our being as humans that we have authority.
“The word becomes important in the Christian Scriptures. Gerhard Kittel, in his masterful Theological Dictionary of the New Testament, writes that exousia ‘is the power displayed in the fact that a command is obeyed.’ From the beginning, authority is related to obedience; authority is not coercive (for the obedience extracted under, for example, torture is hardly true obedience), yet neither is authority constituted by obedience. We might picture authority as a ‘downward’ governance that is ‘displayed,’ but not caused, by an ‘upward’ obedience. According to Kittel’s study, in the New Testament exousia is ‘the power which decides’ but which functions only ‘in a legally ordered whole’ as a power given ultimately by God. Authority is a species of power, namely, a decisive power; nonetheless, the power of authority is never isolated from a divinely authorizing context. Kittel also emphasizes that exousia is active, a performative concept, ‘operative in ordered relationships’ and ‘cannot be separated from its continuous exercise.’ In the Christian community it ‘denote[s] the freedom’ that comes from the community’s divine authorization. But strictly speaking the word means ‘the absolute possibility of action which is proper to God.’ God’s authority, his ‘absolute possibility of action,’ can be seen in many places, including nature and, interestingly, even in God’s tolerance of Satan’s rule, ‘the power of evil . . . [that is] yet encompassed by the divine overruling.’ Christ has divine exousia, his ‘divinely given power and authority to act,’ which is identical with his own freedom, his ‘own rule in free agreement with the Father.’ And exousia is given to the Church as its authority and freedom as the community given ‘existence and nature [by] Christ.’
“What is impressive is the cosmic unity that runs throughout this New Testament concept of authority. All authority comes from God and no thing, no being, no realm is outside his dominion. God’s authority bestows power and freedom and is found preeminently in Christ and, after Christ, in the community that is in him.
“Thus the Christian Scriptures give theological depth to our prior intuitions, sparked by the English and Greek etymologies: that authority has to do with a web of authorizations, and that that has to do with the power or capacity to achieve fullness as a human being.”
— from Victor Lee Austin, Up with Authority: Why We Need Authority to Flourish as Human Beings (T & T Clark, 2010). Austin was interviewed on Volume 107 of the Journal, an interview which was later released as a Friday Feature.