If phenomenal properties do not metaphysically supervene on physical properties, then no reduction of phenomenal properties to physical properties is possible.

Another argument by appeal to a FIST is Chalmers’ appeal to the (putative) metaphysical possibility of zombies (see Section 3.1 and Section 5.4). This is intended to show that phenomenal properties do not metaphysically supervene on, and thus do not reduce to, physical properties. This line of argument is available even though physicalists have not yet proposed any such reduction. If it succeeds, then the project of reducing phenomenal properties to physical properties is doomed to failure.