208 SCIENCE AND THE HUMAN MIND 



thus acquired became developed and intensified by 

 inheritance. Though no direct evidence of such in- 

 heritance could be adduced, it gave a reasonable and 

 consistent working hypothesis for future examination. 



The attention drawn to the effect of environment 

 on the individual, and the extent of the changes which 

 may rightly be attributed to external circumstances, 

 has probably had an enormous influence alike on 

 thought and action. It is difficult to believe that, 

 where the individual can sometimes be modified 

 so profoundly, the species will remain unchanged. 

 Hence, much of the social and philanthropic efforts 

 of the nineteenth century were built up on the theory 

 of modification through environment. 



Two more evolutionists who maintained the direct 

 action of the environment on the individual were 

 fitienne Geoffroy Saint-Hilaire and Robert Chambers, 

 whose anonymous book, Vestiges of Creation, had a 

 great vogue, and helped to prepare men's minds 

 for Darwin. 



But the man to whom Darwin was solely indebted 

 for the central idea of his work, the man who, strange 

 to say, gave the same clue to Wallace also, was the 

 Rev. Thomas Robert Malthus (1766-1834), at one 

 time curate of Albury in Surrey. Malthus, an able 

 economist, lived at the time when the expanding 

 resources of the country, and its need for men to wage 

 a war of existence, made possible and required a great 

 growth of population. In 1798 Malthus published 

 the first edition of the Essay on Population. In it 

 he proclaimed that human population always tends 

 to outrun its means of subsistence, and can only be 

 kept within bounds by famine, pestilence or war, 



