5i8 Edward Livingston Youmans, 



an article upon the subject under the title of The Cause of 

 all Progress, which was objected to as being too assuming. 

 The article was, however, at that time agreed upon, with 

 the understanding that it should be written as soon as the 

 Principles of Psychology w^as finished. The agreement 

 was doomed to be defeated, however, so far as the date 

 was concerned, for, along with the completion of the Psy- 

 chology, in July, 1855, there came a nervous breakdown, 

 which incapacitated Mr. Spencer for labour during a period 

 of eighteen months — the whole work having been written 

 in less than a year. 



We may here note Mr. Spencer's advanced position in 

 dealing with this subject. While yet the notion of Evolu- 

 tion as a process of Nature was as vague and speculative 

 as it had been in the time of Anaximander and Democritus, 

 he had grasped the problem in its universality and its 

 causes, and had successfully applied it to one of the most 

 difficult and important of the sciences. He had traced the 

 operation of the law in the sphere of mind, and placed that 

 study upon a new basis. The conviction is now enter- 

 tained by many that the Principles of Psychology, by Spen- 

 cer, in 1855, is one of the most original and masterly scien- 

 tific treatises of the present century ; if, indeed, it be not 

 the most fruitful contribution to scientific thought that has 

 appeared since the Principia of Newton.* For thousands 



* This association of the name of Spencer with Newton, let it be re- 

 membered, does not rest upon the authority of the present writer ; recent 

 discussions of the subject in the highest quarters are full of it. The Sat- 

 urday Review says : " Since Newton there has not in England been a phi- 

 losopher of more remarkable speculative and systematizing talent than 

 (spite of some errors and some narrowness) Mr. Herbert Spencer." An 

 able writer in the Quarterly Review, in treating of Mr. Spencer's remark- 

 able power of binding together different and distant subjects of thought 

 by the principle of Evolution, remarks : " The two deepest scientific prin- 

 ciples now known of all those relating to material things are the Law of 

 Gravitation and the Law of Evolution." The eminent Professor of Logic in 



