It remains possible, for example, that other people are actually nothing more than automata made out of flesh, referred to by philosophers as philosophical zombies. Perhaps the main argument offered against this possibility in the history of philosophy is the argument from analogy (other things have minds if they are sufficiently similar to us); it can be found in the works of John Stuart Mill, A. J. Ayer, and Bertrand Russell. The argument from analogy has faced scrutiny from the likes of Norman Malcolm who have issues with the "one case" nature of the argument.