“I was an Agnostic. Agnostics didn't have much to argue about.”

Why I Am An Agnostic (1929)
Context: I am an agnostic as to the question of God. I think that it is impossible for the human mind to believe in an object or thing unless it can form a mental picture of such object or thing. Since man ceased to worship openly an anthropomorphic God and talked vaguely and not intelligently about some force in the universe, higher than man, that is responsible for the existence of man and the universe, he cannot be said to believe in God. One cannot believe in a force excepting as a force that pervades matter and is not an individual entity. To believe in a thing, an image of the thing must be stamped on the mind. If one is asked if he believes in such an animal as a camel, there immediately arises in his mind an image of the camel. This image has come from experience or knowledge of the animal gathered in some way or other. No such image comes, or can come, with the idea of a God who is described as a force.

Response when asked whether he called himself an atheist or an agnostic. The Voice of Genius: Conversations with Nobel Scientists and Other Luminaries by Denis Brian (1995), Basic Books, p. 49.
Context: [I call myself] an atheist. Agnostic for me would be trying to weasel out and sound a little nicer than I am about this.

Source: The Ballot or the Bullet (1964), Speech in Cleveland, Ohio (April 3, 1964)

Source: Julian Comstock: A Story of 22nd-Century America (2009), p. 216

Khushwant Singh: "Japji Sahib is Based on the Upanishads

Source: I Am America

Why I Am An Agnostic (1929)
Context: An agnostic is a doubter. The word is generally applied to those who doubt the verity of accepted religious creeds of faiths. Everyone is an agnostic as to the beliefs or creeds they do not accept. Catholics are agnostic to the Protestant creeds, and the Protestants are agnostic to the Catholic creed. Any one who thinks is an agnostic about something, otherwise he must believe that he is possessed of all knowledge. And the proper place for such a person is in the madhouse or the home for the feeble-minded. In a popular way, in the western world, an agnostic is one who doubts or disbelieves the main tenets of the Christian faith.

Surefish interview (2002)
Context: I'm caught between the words 'atheistic' and 'agnostic'. I've got no evidence whatever for believing in a God. But I know that all the things I do know are very small compared with the things that I don't know. So maybe there is a God out there. All I know is that if there is, he hasn't shown himself on earth.
But going further than that, I would say that those people who claim that they do know that there is a God have found this claim of theirs the most wonderful excuse for behaving extremely badly. So belief in a God does not seem to me to result automatically in behaving very well.

Arrowsmith (1925), Ch. 16