PL
This article presents a new argument against mind–body functionalism, strongly inspired by some remarks made by Karl Popper. First, the author presents the original Popperian argument against materialism (from The Self and Its Brain) and its reconstruction by Mariusz Grygianiec. The argument’s conclusion is that if materialism is true, it must also be devoid of any rational grounding. Employing Ned Block’s and Joseph Levine’s accounts of functionalism, the author reformulates the original objection in order to make it a threat to functionalism, which is a more widespread view than the identity theory (which was the aim of Popper’s criticism). The argument proves to be resilient to some potential dangers: Hilary Putnam’s example of the Twin Earth or a duplicate counter-argument mentioned by Block. The conclusion is analogous to the original one: functionalism, provided that it is true, is irrational.