This paper explores R. W. Sperry's view that consciousness is ?causally? effective in directing voluntary human behaviour. This view, formulated in the course of his split brain research, presupposes an earlier theory that motor behaviour is the sole output of the brain and that mental phenomena were developed for regulation of overt response. His view of the ?causal? effectiveness of consciousness is shown to be based on a theory of emergent properties like that of Bunge. It is also shown that (...) Sperry, like Bunge, is a materialist; appearances to the contrary are due to occasional use of standard terms such as ?materialism? and ?interaction? in unusual senses. It is argued, with specific reference to Chisholm and Searle, that Sperry's hypothesis is helpful towards elucidating the structure and dynamics of action. It is also argued that it is not, as Sperry thinks, a consequence of his position that moral values are part of brain science. (shrink)