 Functionalism is a much more widely supported approach to the mental. According to it, mental states are not just a matter of behavior and dispositions, but of causal or other functional relations among sensory inputs, internal states, and behavioral outputs. Note that unless the nature of the internal processing is taken into account as well, functionalism falls to most of the usual objections to behaviorism, for example the ‘homunculus-head’ described in the last section; it therefore seems that any plausible functionalism must take account of internal functions not necessarily reflected in behavioral dispositions. Now, since zombies would satisfy all the functional conditions for full consciousness, functionalism entails that zombies are impossible, although it would obviously be question-begging simply to presuppose functionalism when attacking the zombie idea. However, increasingly sophisticated versions of functionalism are being developed, and any arguments for functionalism are a fortiori arguments against the possibility of zombies. (For some defenses of functionalism against zombies see Dennett 1991; 1995; 1999; Kirk 2017; Shoemaker 1999; Tye 2006; 2008; for doubts about functionalism’s capacity to deal with zombies see for example Harnad 1995.)