- There is probably no general comprehensive theory, but we can make observations.
- Man is competent to be authoritative in virtue of his intelligence. A good authority will have certain qualities and virtues whereas a bad one will lack then. A bad authority is not illegitimate in virtue of his vice or incompetence, but those may lead to actions that delegitimize his authority.
- A father is the legitimate authority in virtue of generation. He may be an idiotic incompetent man, but he is still the authority.
- There is a notion of proximate and remote legitimacy as concerns a continuous line of political authority passed on. Proximately an usurped authority is generally illegitimate for that reason, whereas if this were the case remotely no authority would be legit for its almost certain every political authority has some illegitimate action involved in its establishment.
- The fact that you have reached the age and education to intelligently ask the question is a sign the political authority has provided for the common good to be considered presumptively legit.