 The multiple realizability premise was also part of early arguments for functionalism. Functionalism in the philosophy of mind individuates mental states in terms of their causes and effects. Pain, for example, is caused by tissue damage or trauma to bodily regions, and in turn causes specific beliefs (e.g., that one is in pain), desires (e.g., that one relieves the pain), and behaviors such as crying out, nursing the damaged area, and seeking out pain relieving drugs. Any internal state that mediates a similar pattern of causes and effects is of the mental type pain, regardless of the specific physical mechanisms that realize that pattern of causes and effects in any given case. Ned Block and Jerry Fodor (1972) note that the multiple realizability of mental types on physical types shows that any physicalist type-identity hypothesis will fail to be sufficiently abstract. Functionalism, on the other hand, seems to be at the correct level of abstraction up from explanations of behavior based on physical mechanisms. In particular, it seems sufficiently abstract to handle multiple realizability. Block and Fodor (1972) also note that multiple realizability at the level of physical description is a common characteristic of ordinary functional kinds, like mousetraps and valve lifters. So it appears to be a reasonable empirical hypothesis that characterizing mental kinds as functional kinds is at the correct level of abstraction.