There can be no difference anywhere that doesn’t make a difference elsewhere— no difference in abstract truth that doesn’t express itself in a difference in concrete fact and in conduct consequent upon that fact, imposed on somebody, somehow, somewhere, and somewhen. The whole function of philosophy ought to be to find out what definite difference it will make to you and me, at definite moments on our life, if this world-formula or that world-formula would be true.

– from “What Pragmatism Means” by William James, in Pragmatism, A Reader (1997), edited with introduction by Louis Menand. The essay was originally published in 1907.