“Remember that faith and doubt cannot exist in the same mind at the same time, for one will dispel the other.”

The Star Diaries (1976)

Source: A Circle of Quiet

Variant: Problems cannot be solved with the same mind set that created them.

Vol. I., p. 443.
Anacalypsis (published 1833)

Source: Reason: The Only Oracle Of Man (1784), Ch. III Section IV - Of Physical Evils
Context: Physical evils are in nature inseparable from animal life, they commenced existence with it, and are its concomitants through life; so that the same nature which gives being to the one, gives birth to the other also; the one is not before or after the other, but they are coexistent together, and contemporaries; and as they began existence in a necessary dependance on each other, so they terminate together in death and dissolution. This is the original order to which animal nature is subjected, as applied to every species of it. The beasts of the field, the fowls of the air, the fishes of the sea, with reptiles, and all manner of beings, which are possessed with animal life; nor is pain, sickness, or mortality any part of God's Punishment for sin. On the other hand sensual happiness is no part of the reward of virtue: to reward moral actions with a glass of wine or a shoulder of mutton, would be as inadequate, as to measure a triangle with sound, for virtue and vice pertain to the mind, and their merits or demerits have their just effects on the conscience, as has been before evinced: but animal gratifications are common to the human race indiscriminately, and also, to the beasts of the field: and physical evils as promiscuously and universally extend to the whole, so "That there is no knowing good or evil by all that is before us, for all is vanity." It was not among the number of possibles, that animal life should be exempted from mortality: omnipotence itself could not have made it capable of externalization and indissolubility; for the self same nature which constitutes animal life, subjects it to decay and dissolution; so that the one cannot be without the other, any more than there could be a compact number of mountains without valleys, or that I could exist and not exist at the same time, or that God should effect any other contradiction in nature...

Rome, or Reason? A Reply to Cardinal Manning. Part I. The North American Review (1888)

Source: The State of the World 2010, public lecture in New York City, USA, (July 2010)

[NewsBank, Bill Nye , ‘the science guy,’ vs. Marsh Blackburn, the climate change skeptic congresswoman, Knoxville News Sentinel: Blogs, Knoxville, Tennessee, February 17, 2014]