Neural plasticity — the fact that areas of the brain can assume the functions of other parts that have been damaged as the result of traumatic injury, pathology, natural biological development, or other processes — has long been considered to be an example.
Jerry Fodor (1975) deployed multiple realizability more generally as an argument against any reductionist account of the relation between higher-level sciences and physics.
Given generalized multiple realizability, the physical science part of these psychophysical bridge laws will end up being a (possibly infinite) disjunction of all the terms referring to possible physical realizations of a mental kind.
As a result of these arguments and others that build upon them, the dominant theory in philosophy of mind since the 1960s has been a version of non-reductive physicalism based on multiple realizability.
[11] Putnam cites examples from the animal kingdom as evidence for the multiple realizability of mental states.
[7] Putnam concludes that type-identity and other reductive theories make an extremely "ambitious" and "highly implausible"[citation needed] conjecture that can be disproven with just one example of multiple realizability.
Starting with David Kellogg Lewis, many reductionists argued that it is very common in scientific practice to reduce one theory to another via local, structure-specific reductions.
One criticism of multiple realizability is that any theory that attempts to address the possibility of generalized multiple realizability must necessarily be so local and context-specific in nature (referring exclusively to a certain token system of a certain structure-type at a certain time) that its reductions would be incompatible with even a minimally acceptable degree of generality in scientific theorizing.
The similarity (produced by homology or convergent evolution) of brain structures allows us to generalize across species.
Sungsu Kim has recently responded to this objection using the distinction between homology of brain structures and homoplasy.
Homologies are characteristics of physiology, morphology, behavior, or psychology shared by two or more species and inherited from a common ancestor.
Homoplasies are similar or identical characteristics shared by two or more species but not inherited from a common ancestor, having evolved independently.
The only way to empirically test the thesis of multiple realizability would be to examine brain structures and determine whether some homoplasious "psychological processes or functions might be 'constructed' from different material" and supported by different brain structures just as the flight capacities of bats and birds emerge from different morphophysiologies.
The emergence of similar behavioral outputs or psychological functions brought about by similar or identical brain structures in convergent evolutionary lineages would provide some evidence against multiple realizability, since it is highly improbable that this would happen, if not for constraints on the type of physical system that can realize mental phenomena.
This, however, would not completely refute the possibility of realizability of mental states in radically different physical systems such as non-carbon based life forms or machines.
Alan Turing remarked on multiple realizability in 1950, for example,[18] writing: "The fact that Babbage's Analytical Engine was to be entirely mechanical will help us rid ourselves of a superstition.