“Scientist believe in things, not in person”

The second sentence is often misquoted as “Science has proof without any certainty. Creationists have certainty without any proof.” or “Religion gives us certainty without proof; science gives us proof without certainty.”
Context: Bigotry and science can have no communication with each other, for science begins where bigotry and absolute certainty end. The scientist believes in proof without certainty, the bigot in certainty without proof. Let us never forget that tyranny most often springs from a fanatical faith in the absoluteness of one’s beliefs.

Source: The Evolution of Civilizations (1961) (Second Edition 1979), Chapter 1, Scientific Method and the Social Sciences, p. 34

Source: What Is Life? with Mind and Matter and Autobiographical Sketches

Source: Freakonomics: A Rogue Economist Explores the Hidden Side of Everything

Quasar, Quasar, Burning Bright (1978), p. 235
General sources

Emperor Has No Clothes Award acceptance speech (2003)
Context: I am a reasonably emotional person, and I see no reason why that's incompatible with being a scientist. Even if we learn about how everything works, that doesn't mean anything at all. You can reduce how an impala leaps to a bunch of biomechanical equations. You can turn Bach into contrapuntal equations, and that doesn't reduce in the slightest our capacity to be moved by a gazelle leaping or Bach thundering. There is no reason to be less moved by nature around us simply because it's revealed to have more layers of complexity than we first observed.
The more important reason why people shouldn't be afraid is, we're never going to inadvertently go and explain everything. We may learn everything about something, and we may learn something about everything, but we're never going to learn everything about everything. When you study science, and especially these realms of the biology of what makes us human, what's clear is that every time you find out something, that brings up ten new questions, and half of those are better questions than you started with.

Pt. 1, Ch. 10
Disturbing the Universe (1979)

Source: Life of Pi