It appears to me that in this world all things move onwards together, and that just as in things external, and what we are accustomed to call material, so in things which concern the mind, there is no department of philosophy, or science, or art which goes on quite by itself, without influencing and being influenced by the progress which goes on in other lines. The tone and predisposition of men's minds, and the character of the prevalent courses of speculation, seems to be determined by causes which affect all branches of mental activity in a similar way, and the tendencies which show themselves strongly and effectively in one branch are sure to appear sooner or later in another.