434 Edward Livingston Youmans. 



which do not occur at all in those of inorganic nature. As, for in- 

 stance, the idea of predisposition, and of predisposing causes, as dis- 

 tinguished from exciting causes. The operation of all moral forces 

 is immensely influenced by predisposition : without that element, it is 

 impossible to explain the commonest facts of history and social life. 

 Physiology is also the first science in which we recognize the influ- 

 ence of habit the tendency of something to happen again merely 

 because it has happened before. From physiology, too, we get our 

 clearest notion of what is meant by development or evolution. The 

 growth of a plant or animal from the first germ is the typical speci- 

 men of a phenomenon which rules through the whole course of the 

 history of man and society increase of function, through expansion 

 and differentiation of structure by internal forces. I cannot enter 

 into the subject at greater length ; it is enough if I throw out hints 

 which may be germs of further thought in yourselves. Those who 

 aim at high intellectual achievements may be assured that no part of 

 their time will be less wasted, than that which they employ in be- 

 coming familiar with the methods and with the main conceptions of 

 the science of organization and life. 



Physiology, at its upper extremity, touches on Psychology, or the 

 Philosophy of Mind ; and without raising any disputed questions 

 about the limits between Matter and Spirit, the nerves and brain are 

 admitted to have so intimate a connection with the mental opera- 

 tions, that the student of the last cannot dispense with a consider- 

 able knowledge of the first. The value of psychology itself need 

 hardly be expatiated upon in a Scottish university ; for it has always 

 been there studied with brilliant success. Almost everything which 

 has been contributed from these islands toward its advancement 

 since Locke and Berkeley has, until very lately, and much of it even 

 in the present generation, proceeded from Scottish authors and Scot- 

 tish professors. Psychology, in truth, is simply the knowledge of the 

 laws of human nature. If there is anything that deserves to be 

 studied by man, it is his own nature and that of his fellow-men : and 

 if it is worth studying at all, it is worth studying scientifically, so as 

 to reach the fundamental laws which underlie and govern all the rest. 

 With regard to the suitableness of this subject for general education, 

 a distinction must be made. There are certain observed laws of our 

 thoughts and of our feelings which rest upon experimental evidence, 

 and, once seized, are a clue to the interpretation of much that we are 



