Friendly thoughts on thoughtful friendliness

Abstract

We discuss Wiseman, Cavalcanti and Rieffel's "thoughtful" local friendliness no-go theorem and the experimental programme they propose to test local friendliness inequalities. We argue that, to prove the theorem, the assumptions need to be strengthened to exclude the possibility of variable numbers of thoughtful agents existing in different phases of the experiment. We argue further that this possibility may arise naturally, even in one-world versions of quantum theory. We also query whether the motivations they give for their assumptions hold up well under their definition of "thoughtfulness" as displaying human-level cognitive ability, and suggest that their justification requires replacing "thoughtfulness" by "consciousness" or "conscious thoughtfulness".