A key change occurred in Rotblat’s thinking at this time. He realized that the argument to develop nuclear weapons that permitted him to work on them, that is, the argument for deterrence, was false. It would not have worked with Hitler, because Hitler would have used such weapons in spite of any consequences. Rotblat’s own reasoning in favour of working on nuclear weapons was invalid. He proposed what looks like a naive idea: that there should be a moratorium on research related to nuclear weapons. He talked to his colleagues in Liverpool, knowing this to be a drastic plan; nevertheless it seems that it had a warm reception.

Martin Underwood, Joseph Rotblat: a man of conscience in the nuclear age, Brighton [England] ; Portland, Or, 2009, p. 43