Thus Mill asserted that if the advanced thinkers who are engaged on the subject succeed in discovering an empirical law from the data of history, it may be converted into a scientific law by deducing it a priori from the principles of human nature.  In the meantime, he argued that what is already known of those principles justifies the important conclusion that the order of general human progression will mainly depend on the order of progression in the intellectual convictions of mankind.

Throughout his exposition Mill uses “progress” in a neutral sense, without implying that the progression necessarily means improvement.  Social science has still to demonstrate that the changes determined by human nature do mean improvement.  But in warning the reader of this he declares himself to be personally an optimist, believing that the general tendency, saving temporary exceptions, is in the direction of a better and happier state.

8.

Twenty years later [Footnote:  In later editions of the Logic.] Mill was able to say that the conception of history as subject to general laws had “passed into the domain of newspaper and ordinary political discussion.”  Buckle’s history of civilisation in England [Footnote:  2 Vol. i. appeared in 1857, vol. ii. in 1861.] which enjoyed an immediate success, did a great deal to popularise the idea.  In this stimulating work Buckle took the fact of Progress for granted; his purpose was to investigate its causes.  Considering the two general conditions on which all events depend, human nature and external nature, he arrived at two conclusions:  (1) In the early stage of history the influence of man’s external environment is the more decisive factor; but as time goes on the roles are gradually inverted, and now it is his own nature that is principally responsible for his development. (2) Progress is determined, not by the emotional and moral faculties, but by the intellect; [Footnote:  This was the view of Jouffroy, Comte, and Mill; Buckle popularised it.] the emotional and moral faculties are stationary, and therefore religion is not a decisive influence in the onward movement of humanity.  “I pledge myself to show that the progress Europe has made from barbarism to civilisation is entirely due to its intellectual activity. . . .  In what may be called the innate and original morals of mankind there is, so far as we are aware, no progress.” [Footnote:  Buckle has been very unjustly treated by some critics, but has found an able defender in Mr. J.M.  Robertson (Buckle and his Critics (1895)).  The remarks of Benn (History of Rationalism in the Nineteenth Century, ii. 182 sqq.) are worth reading.]