Idealists, realists, and politicians.

From G.K. Chesterton's The Paradoxes of Mr. Pond.

For the true idealist and the real realist have at least the love of action in common. And the practical politician thrives by offering practical objection to any action. What the idealist does may be unworkable and what the man of action does may be unscrupulous; but in neither trade can a man win a reputation by doing nothing.