 Experimental philosophy does not know what its work will yield or fail to yield; but it works without pause. On the contrary, rational philosophy weighs the possibilities, makes pronouncements, and stops there. It boldly declares, light cannot be decomposed; experimental philosophy listens, and remains silent for centuries; then suddenly shows us the prism, and declares, light is decomposed. (IN, § XXIII; DPV IX: 43–44; his emphasis)