His own early thinking addressed questions of value. In The Moral Economy (1909) he outlined his Principle of Inclusiveness. One of his illustrations of this "quantitative" principle was that a man who liked cats and dogs had a more inclusive interest than a woman who only liked canaries. The more inclusive interest was the more valuable. He participated in the New Realism movement of the times, which posited the externality of the world. That is the world does not depend on being known, which was the idealist opposite of the realist position.
The war deepened his thinking, as it so often does in history. He published The present conflict of ideals: a study of the philosophical background of the world war. (1922) We excerpt this text:
THE CONFUSION OF VALUES
I have failed so far to allude to a more serious defect in this idealistic optimism. It is not only hollow, as I have already contended, but it is misleading and confusing. Through its eagerness to identify reality and value it blurs and compromises human ideals. This effect is further aggravated by what I have termed its "monism of values." There is to be only one type of perfection into which truth, goodness, beauty and every other good thing are all resolved. Now I should like to call attention to the fact that there are two ways of making things look alike. One way is by clear discrimination and segregation, classifying like with like. The other way is by turning down the lights. In the dark, it is said, all cats are gray. So in the twilight of ambiguity all ideals may look alike. But that is only because they have all lost their coloring. The idealist in striving to show that reality satisfies every human aspiration succeeds only by eliminating whatever is specific and peculiar in every human aspiration. The result is that you get a sort of conjunct perfection which is totally perfect because it is not perfect in respect of any one of the definite standards of life.
The book mentioned above illustrates an effort to fix the defects in thinking which allowed the war. Although Perry assumes the idealists were at fault, in fact, by assuming it was ideas which caused the war, he himself betrays idealistic assumptions.
We have not mentioned much of his bibliography. I want to spend more time sometime with his revision of Alfred Weber’s History of Philosophy (1925). Perry deserves more attention outside his relation to William James.