by different realizers. For example, both a winged corkscrew and a waiter's corkscrew have the property of removing corks and do so through the same mechanism — a screw and pull mechanism. Because the mechanism is fundamentally unchanged, the property is variably realizable. For a property to be multiply realizable, the property must be able to be instantiated by different realizers and different mechanisms. The classic spring mousetrap and the glue mousetrap instantiate the same property, the ability to trap mice, but they do so through different mechanisms. As such, the property is multiply realizable. A property is medium independent if it can be instantiated by different realizers and different mechanisms and if the inputs and outputs of the mechanisms are also multiply realizable. A mousetrap is not medium independent; it must take a mouse as an input. A computer, though, is medium independent. A computer can be constructed from different parts assembled into different mechanisms and can take different types of inputs and outputs. In typical digital computers, the inputs and outputs are voltages, but in quantum computers, the inputs and outputs would be different. The significance of multiple realizability Multiple realizability has been used as an argument against type-identity theory, against reductionist theories of mind in general, for functionalist theories of mind, and even against functionalist theories of mind. Starting in the 1960s, Hilary Putnam used multiple realizability as an argument against type-identity theory. Specifically, Putnam noted that the multiple realizability of pain entails that, contrary to type-identity theory, pain is not identical to C-fibre firing. More generally, multiple realizability shows that psychological attributes are not the same as physical attributes. Psychological attributes, rather, are disjunctions of physical attributes. Fodor, Putnam, and others noted that, along with being an effective argument against type-identity theories, multiple realizability implies that any low-level explanation of higher-level mental phenomena would be insufficiently abstract and general. Jerry Fodor (1975) deployed multiple realizability more generally as an argument against any reductionist account of the relation between higher-level sciences and physics. Fodor also uses multiple realizability to argue against reductionism not only of psychology but of any special sciences (that is, any sciences that are "higher level" than physics). In his characterization of reductionism, all mental kind predicates in an ideal and completed psychology must correspond with physical kind predicates in an ideal and completed physics. He suggests taking Ernest Nagel's theory of reduction, which