Power corrupts, we know, but it's not often a question of straightforward embezzlement or preferential treatment of friends.
No, it's rare for the powerful to feel corrupted. They will be sure what they are doing is unfortunate but necessary, or perhaps even necessary and good, but nevertheless, they have lowered their ethical standards to enjoy the thrill, the buzz of exercising power.
So we turn to President Obama and Syria. Surely his advisers have told him that Syria is not Libya (or Iraq), Assad is not Gaddafi (or Saddam Hussein).
Or perhaps not. The circles in which he moves have changed.
Nevertheless, it is a pretty obvious example. And as the rhetoric is ratcheted higher and higher, the gap between his former ideals and the realities of holding power become ever more exposed.
And, for those who dismiss such sentimental nonsense, the fact is US action without clear, explicit UN backing, apart from worsening the Syrian civil war, will not be in the long-term interests of the USA. It will persuade China, and remind Russia, that to counter the US's ability to act without or even in the face of UN approval needs more than soft power. It needs a big stick.