As to the falsity of the outer world, Nietzsche sometimes uses strong language, but it is exact from his point of view: it is a "product of fantasy," a "world of phantoms," "poetry," "the primitive poetry of mankind" (Werke, XII, 36, § 69; 170, § 351; Dawn of Day, § 118). He thinks that whatever may be our philosophical standpoint [ordinary realism he hardly considers as a philosophical standpoint], this falsity (Irrthümlichkeit) is the surest and solidest thing we can still lay hold of (Beyond Good and Evil, § 34). Riehl asks (op. cit., p. 130) how we can speak of falsity, if we do not know the truth; but one is a negative, the other a positive judgment—Nietzsche himself observes that the destruction of an illusion does not of itself give us the truth, but may simply make the field of our ignorance wider (Werke, XIII, 138, § 318; Will to Power, § 603). The illusoriness of the physical world has been often asserted, e.g., by Hume, of whom Norman Kemp Smith says, "Hume's argument rests throughout on the supposition that perishing subjective states are the only possible objects of mind, and that it is these perishing states which natural belief constrains us to regard as independent existence. Such belief is obviously, on the above interpretation, sheer illusion and utterly false" (Mind, April, 1905, pp. 169, 170). See also Ralph Barton Perry's admirable statement of Hume's view, Present Philosophical Tendencies, pp. 138-9. It is curious that Nietzsche refers rarely to Hume, and but twice to a critical point in his philosophy, viz., his conception of causality (Werke, XIV, 27, § 49; XVI, 51). His general view, however, might well receive the epithet, "psychologism" with which Perry characterizes Hume's view—or even a stronger and still more barbarous one, viz., "biographism," for he says, "Man may reach out as far as he will with his knowledge and seem to himself as objective as possible—in the end he gets nothing from it but his own biography" (Human, etc., § 513).