 Einstein’s conviction that the theoretical physicist must trust simplicity is that his work was moving steadily into domains ever further removed from direct contact with observation and experiment. Einstein started to routinely claim that this was the lesson he had drawn from the way in which he had found general relativity (Norton 2000). There are, however, good reasons to think that Einstein’s selective recollections (Jannsen and Renn 2007) were instrumental to his defense of relying on a purely mathematical strategy in the search for a unified field theory (van Dongen 2010): 