Our opinion of the gods and our knowledge of men lead us to conclude that it is a general and necessary law of nature to rule whatever one can. This … - Thucydides

Of the gods we believe, and of men we know, that by a necessary law of their nature they rule wherever they can. And it is not as if we were the first to make this law, or to act upon it when made: we found it existing before us, and shall leave it to exist for ever after us; all we do is to make use of it, knowing that you and everybody else, having the same power as we have, would do the same as we do.

Of the gods we believe, and of men we know, that by nature they desire to rule.

Of the gods we believe, and of men we know, that by a necessary law of their nature they rule wherever they can.

not only of the Hellenes, but of a large part of the barbarian world

If you have the power to put a stop to subjugation, yet look the other way while it happens, then you have done it yourselves,

Goodwill shown by the party that is asking for help does not mean security for the prospective ally. What is looked for is a positive preponderance of power in action.