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. Historical note Observations of multiple realizability — and of its relation to functionalism — predate their use in philosophy beginning in the 1960s. Alan Turing remarked on multiple realizability in 1950, for example, writing: "The fact that Babbage's Analytical Engine was to be entirely mechanical will help us rid ourselves of a superstition. Importance is often attached to the fact that modern digital computers are electrical, and the nervous system is also electrical. Since Babbage's machine was not electrical, and since all digital computers are in a sense equivalent, we see that this use of electricity cannot be of theoretical importance. ... If we wish to find such similarities we should look rather for mathematical analogies of function." Notes References Putnam, Hilary. Representation and Reality. 1988. Cambridge, MA: MIT Press. Fodor, Jerry. The Language of Thought. 1975. New York. Thomas Cromwell. Further reading External links PhilPapers bibliography on multiple realizability Arguments in philosophy of mind Cognitive science