George Lakoff, a professor of linguistics at the University of California, Berkeley, is the author of, most recently, "The Political Mind: A Cognitive Scientist's Guide to Your Brain and Its Politics."

When are you “lying”? When you make, or purposely convey, a statement that you believe to be false, a statement intended to deceive someone to gain, or not lose, some advantage, and which must in fact be false. You can also lie by naming (“the job creators,” “death panels”) or by purposely evoking a false framing of a situation.

If accused of lying, you have excuses available: an understandable mistake, a white lie (harmless, technically false, intended to help), an uncharitable interpretation (not what I meant), a disagreement about word meaning (what is a “lobbyist”?), a misstatement (an innocent mistake in word choice), a social lie (What a pleasure to be here in Iowa in midwinter!), a technically true statement that indirectly entails a lie, a false statement you believed to be true at the time, a rhetorical statement (an innocent exaggeration, understatements, metaphor, etc.), an alternative framing, and so on. These can be either honest, or lying to get out of a lie.

Politicians lie to protect or advance what they see as a moral endeavor, like invading Iraq or cutting off 'welfare queens.'

All politics is moral. Politicians advocate positions that they claim are right, not wrong or morally neutral. Like anyone else, a politician may lie to protect his or her own skin. But more often politicians lie to protect or advance what they see as a moral endeavor (e.g., the invasion of Iraq, Reagan’s war on nonexistent “welfare queens,” Johnson on the Tonkin Gulf). In the conservative moral system, the highest value is protecting and extending the moral system itself. When conservative icons or ideas themselves are threatened, it is not uncommon for conservative politicians to lie in their defense (Reagan never raised taxes; there’s no evidence for global warming; “government takeover”).

Voters tolerate lies they see as serving a moral purpose, or as having a reasonable excuse. They give more latitude to politicians they identify with.