An atheist lacks faith in God, believes there is no god, or lacks awareness of gods. An agnostic either believes that it is impossible to know whether there is a god or is noncommittal on the issue. The difference may seem small, but atheism and agnosticism are actually vastly different worldviews. To claim there is no point in trying to prove or disprove God’s existence (as many philosophers have done) is to acknowledge the limits of human perception. To take the bold stance that there definitely is no god (as a few philosophers have done) implies that human perception is not so limited and that we can make such claims about the universe. These positions (as well as the position that God does exist) give rise to fundamentally disparate philosophies.
Atheist is generally confined to this nonbelief-related sense, but agnostic has another definition—namely, one who is doubtful or noncommittal. It also serves as an adjective meaning doubtful or noncommittal. For example, these writers use agnostic in the sense unrelated to belief in God.
Atheists and agnostics are often lumped together as one group—namely, those who lack faith in a god—but it’s important to remember that these terms, especially agnostic, cover a broad spectrum of views. And the terms do not necessarily imply irreligion. Some Buddhists, for example, are atheists, and there is a strong tradition of agnostic thought in Hinduism.