He also worked to elaborate and extend Darwin and his ideas on natural selection. However, Wallace also realized that the scope and claim of the theory was limited. Darwin himself had limited it. In examining this aspect, excluded ab initio by Darwin, Wallace came to the conclusion that Life itself cannot be understood except by means of a theory that includes "an organising and directive Life-Principle." These necessarily involve a "Creative Power", a "directive Mind" and finally "an ultimate Purpose" (the development of Man). It supports the view of John Hunter that "life is the cause, not the consequence" of the organisation of matter. Thus, life precedes matter and when it infuses matter, forms living matter (protoplasm). Wallace then refers to the operation of another power called "mind" that utilizes the power of life and is connected with a higher realm than life or matter: Proceeding from Hunter's view that Life is the directive power above and behind living matter, Wallace argues that logically, Mind is the cause of consciousness, which exists in different degrees and kinds in living matter. Emergent evolution Early roots The issue of how change in nature 'emerged' can be found in classical Greek thought - order coming out of chaos and whether by chance or necessity. Aristotle spoke of wholes that were greater than the sum of their parts because of emergent properties. The second-century anatomist and physiologist Galen also distinguished between the resultant and emergent qualities of wholes. (Reid, p. 72) Hegel spoke of the revolutionary progression of life from non-living to conscious and then to the spiritual and Kant perceived that simple parts of an organism interact to produce a progressively complex series of emergences of functional forms, a distinction that carried over to John Stuart Mill (1843), who stated that even chemical compounds have novel features that cannot be predicted from their elements. [Reid, p. 72] The idea of an emergent quality that was something new in nature was further taken up by George Henry Lewes (1874–1875), who again noted, as with Galen earlier, that these evolutionary "emergent" qualities are distinguishable from adaptive, additive "resultants." Henry Drummond in The Descent of Man (1894) stated that emergence can be seen in the fact that the laws of nature are different for the organic or vital compared to the inertial inorganic realm. As Reid points out, Drummond also realized that greater complexity brought greater