I also loved that chapter. Deutsch really argues for Popper's "conjecture and refutation" model of science (or as he renamed it, "conjecture and criticism") an

I also loved that chapter. Deutsch really argues for Popper's "conjecture and refutation" model of science (or as he renamed it, "conjecture and criticism") and one of the great points he makes is that both those processes can be done entirely in the mind. Physical evidence may be necessary for some kinds of criticism, but sometimes reason alone can produce useful criticism.