BIOLOGY AND SOCIOLOGY 71 



the last half-century, or so it seems to me, is the 

 recognition that mind is not to be explained away as 

 a mere epiphenomenon, but is to be studied as a 

 phenomenon. From this point of view, bjology 

 will always be the connecting link between physico- 

 chemical science on the one hand, and psychology 

 on the other. There is every reason to suppose and 

 no reason to doubt that life, which we know to be 

 composed of the same material elements and to work 

 by the same energy as non-living matter, actually 

 arose from it during the evolution of this planet. 

 There is, in the behaviour of the lower organisms, 

 nothing which by itself would make us postulate 

 mind : but in the higher insects, molluscs, and 

 vertebrates, the last in particular, mental process is not 

 only clearly present, but clearly of great biological 

 importance ; and finally the mind of man, according 

 to innumerable converging lines of evidence, has 

 evolved from the mind of some non-human mammal. 

 The principle of continuity makes us postulate 

 that this new category of phenomena has not sprung 

 up during the course of evolution absolutely de novo^ 

 but that it is in some sense universally present in 

 all phenomena. It is merely that we have not yet 

 found a method for the direct detection of mental 

 processes as we have, say, for electrical processes ; 

 but something of the same general nature, the same 

 category as mind must, if we wish to preserve our 

 scientific sanity, our belief in the orderliness of the 



