I doubt that anyone does not really believe in God. People may think they don’t have any belief, but you will usually find that somewhere down in a human being’s soul there is a belief in something beyond himself. In any case, I would not judge a man’s character by his belief or unbelief. I would judge his character by his deeds; and no matter what he said about his beliefs, his behavior would soon show whether he was a man of good character or bad.

Eleanor Roosevelt (1884–1962) American politician, diplomat, activist; First Lady of the US (1933–45)

Column (1956-08), “If You Ask Me,” McCall’s Magazine, Vol. 83
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When asked, "What standards do you use to judge a man's character when you know he doesn't believe in God?"

A slightly shortened version of this is sometimes given, e.g., in Carol Kelly-Gangi (ed.), Franklin and Eleanor Roosevelt: Their Essential Wisdom (2014): "[...] People may think they don’t have any belief, but you will usually find that there is a belief in something beyond himself. [...]"