 The substance of this essay was first published in Mind in 1879 and in the Princeton Review in 1882, and then republished in The Will to Believe and Other Essays in Popular Philosophy in 1897. Although he never quite says that rationality is a sentiment, James holds that a sentiment—really a set of sentiments—is a “mark” of rationality. The philosopher, James writes, will recognize the rationality of a conception “as he recognizes everything else, by certain subjective marks with which it affects him. When he gets the marks, he may know that he has got the rationality.” These marks include a “strong feeling of ease, peace, rest” (WB 57), and a “feeling of the sufficiency of the present moment, of its absoluteness” (WB 58). There is also a “passion for parsimony” (WB 58) that is felt in grasping theoretical unifications, as well as a passion for distinguishing, a “loyalty to clearness and integrity of perception, dislike of blurred outlines, of vague identifications” (WB 59). The ideal philosopher, James holds, blends these two passions of rationality, and even some great philosophers go too far in one direction or another: Spinoza’s unity of all things in one substance is “barren,” as is Hume’s “‘looseness and separateness’ of everything…” (WB 60).