“The strange thing about the theory of evolution is that everyone thinks he understands it. But we do not. A biosphere, or an econosphere, self-consistently coconstructs itself according to principles we do not yet fathom.”

Source: Snow Falling on Cedars

"Heretical Thoughts about Science and Society", in Edge (8 August 2007) http://www.edge.org/documents/archive/edge219.html#dysonf
Context: My first heresy says that all the fuss about global warming is grossly exaggerated. Here I am opposing the holy brotherhood of climate model experts and the crowd of deluded citizens who believe the numbers predicted by the computer models. Of course, they say, I have no degree in meteorology and I am therefore not qualified to speak. But I have studied the climate models and I know what they can do. The models solve the equations of fluid dynamics, and they do a very good job of describing the fluid motions of the atmosphere and the oceans. They do a very poor job of describing the clouds, the dust, the chemistry and the biology of fields and farms and forests. They do not begin to describe the real world that we live in. The real world is muddy and messy and full of things that we do not yet understand. It is much easier for a scientist to sit in an air-conditioned building and run computer models, than to put on winter clothes and measure what is really happening outside in the swamps and the clouds. That is why the climate model experts end up believing their own models.

Section 57
The True Believer (1951), Part Three: United Action and Self-Sacrifice
Context: We can be absolutely certain only about things we do not understand. A doctrine that is understood is shorn of its strength.

Book Two, Part III “The Dark City”, Chapter 3 (p. 200)
The Birthgrave (1975)

Source: Dictionary of Burning Words of Brilliant Writers, P. 286.

Sex, Ecology, Spirituality (1995, 2000)

Last lines. Hawking later wrote: "In the proof stage I nearly cut the last sentence in the book... Had I done so, the sales might have been halved.
Black Holes and Baby Universes and Other Essays (1993)

Source: Economic Philosophy (1962), p. 21

Source: The Myth of Male Power (1993), Part III: Government as substitute husband, p. 336.