A popular argument supporting functionalism has been what is commonly called the “multiple realizability” argument. One version of this argument uses thought experiments designed to show that minds could be composed of different types of material. This article offers a metaphilosophical analysis of this argument and shows that it fails to provide a strong case for functionalism. The multiple realizability argument is best understood as an inference-to-the-best-explanation argument, whereby a functionalist account of our mental concepts serves to explain our multiple realizability intuitions. I show that the argument is inadequate because alternative accounts of our mental concepts exist that provide equally plausible explanations for these intuitions. Moreover, in the case of our qualia concepts, a nonfunctionalist account explains several other intuitions that functionalism cannot explain. Thus, despite its popularity, the intuition-based version of the multiple realizability argument is a poor reason for accepting functionalism.