An atheist, like a Christian...

An atheist, like a Christian, holds that we can know whether or not there is a God. The Christian holds that we can know there is a God; the atheist, that we can know there is not. The agnostic suspends judgment, saying that there are not sufficient grounds either for affirmation or for denial...an agnostic may hold that the existence of God, though not impossible, is very improbable; he may even hold it so improbable that it is not worth considering in practice.

--Bertrand Russell