Lucian of Samosata

The good historian, then, must be thus described: he must be fearless, uncorrupted, free, the friend of truth and of liberty; one who, to use the words of the comic poet, calls a fig a fig, and a skiff a skiff, neither giving nor withholding from any, from favour or from enmity, not influenced by pity, by shame, or by remorse; a just judge, so far benevolent to all as never to give more than is due to any in his work; a stranger to all, of no country, bound only by his own laws, acknowledging no sovereign, never considering what this or that man may say of him, but relating faithfully everything as it happened.

Lucian, “How to Write History.” Thomas Francklin, D.D. (trans.).