“Let's say that you have an incredible one percent of all the knowledge in the universe. Would it be possible, in the ninety-nine percent of the knowledge that you haven't yet come across, that there might be ample evidence to prove the existence of God? If you are reasonable, you will be forced to admit that it is possible.”

Source: Entwined with You

Ron English's Fauxlosophy: Volume 2 (2022)

Spoken statement (c. 1903); published in Harper's Monthly (September 1932).
Variants:
None of my inventions came by accident. I see a worthwhile need to be met and I make trial after trial until it comes. What it boils down to is one per cent inspiration and ninety-nine percent perspiration.
Statement in a press conference (1929), as quoted in Uncommon Friends: Life with Thomas Edison, Henry Ford, Harvey Firestone, Alexis Carrel & Charles Lindbergh (1987) by James D. Newton, p. 24.
Variant forms without early citation: "Genius is one percent inspiration and ninety-nine percent perspiration. Accordingly, a 'genius' is often merely a talented person who has done all of his or her homework."
"Genius: one percent inspiration and 99 percent perspiration."
1900s
Variant: Genius is one per cent inspiration and ninety nine perspiration.

Source: The Four Pillars of Investing (2002), Chapter 15, A Final Word, p. 297.

Prayers For The Assassin (2006)

As quoted in The Roosevelt I Knew (1946) by Frances Perkins, p. 5
Posthumous publications

On Guard: Defending Your Faith with Reason and Precision (2010), p. 149

Attributed