ON HUMAN NATURE AND ITS CAPACITIES FOR VIRTUE. 87 



knowledge of the human subject ; they failed to create 

 a science and a code of ethics because, even if human 

 conduct can be reduced to rule and system a point not 

 without doubt still the subordinate sciences had not 

 been created or sufficiently far developed to furnish solid 

 principles and reliable clues through the complexities of 

 human nature and human affairs. 



They did not know the human subject : they did not 

 know, as we do to-day from the principles of physiology, 

 the close dependence of our mental and even of our moral 

 life upon the bodily material basis a truth which finds 

 its chief weight and application in the free-will contro- 

 versy, and the apportionment of moral responsibility, but 

 which is not without its significance or importance here, 

 where the nature and limits of virtue are under con- 

 sideration. They did not know that thought, emotion, 

 and volition, the trinity in unity that on the inner side 

 make the man and compose the contents of his conscious- 

 ness, are all, in a certain extremely important though 

 not definitely measurable sense, functions of the brain 

 and nervous system, of the general bodily health and 

 finally of the quality of the blood ; that they vary both 

 in degree of perfection and in amount with our varying 

 bodily states, so much so that an impoverishment of 

 the blood will starve simultaneously the thought and 

 emotions, and will weaken or paralyze the strongest 

 will ; that a prolonged and sustained strain on the brain 

 and nervous system will make "all the uses of this 

 world " seem " weary, stale, flat, and unprofitable," may 

 convert the whole circle and content of consciousness 

 into a perpetual sea of troubles, where virtue and vice 

 are scarcely distinguishable, or seem only matter of 

 opinion, where "nothing is either good or bad, but 

 thinking makes it so ; " and that finally, if the nerve 



