From Urban Dictionary: Crimestop refers to the ability to stop short of any thought that might be heretical or unorthodox before it is even thought, as if by instinct. It is the ability to misunderstand analogies, fail to perceive logical errors, and be repelled or bored by any train of thought or conversation that might be inimical to Ingsoc. Of course, this process is not unique to Ingsoc, and has been and still is applied by most religious and political extremists.
Crimestop is not stupidity, or at least not natural stupidity. It is the ability to deliberately retard one’s own intelligence, and, of course, to forget the process of doing it by doublethink.
“He was troubled by false memories occasionally. They did not matter so long as one knew them for what they were.”