The nature and plausibility of mind-brain reductionism depends upon the underlying account of reduction adopted. There have been at least four distinct stages in the development of mind-brain reductionism over its first half-century, and only two of these stages made any real use of actual neuroscientific discoveries. This chapter briefly articulates each stage in the development of mind-brain reductionism. It explores to what extent proponents at that stage appealed explicitly to then current neuroscience in order to defend the truth of mind-brain reductionism and to what extent did the neuroscience of the time affect the account that philosophical reductionists adopted of what reduction is. The initial stage of mind-brain reductionism rested on mid-twentieth-century philosophy's emphasis on linguistic analysis and on a view of contingent identity that are no longer prominent. By the mid 1990s consciousness had made a serious comeback in both philosophy of mind and the cognitive sciences.