Inductive inference is the fundamental method of modern Metaphysical Realism. At one time it was thought that out of concepts we could evolve something that would no longer be a concept. It was thought that the metaphysical reals, which Metaphysical Realism after all requires, could be known by means of concepts. This method of philosophising is now out of date. Instead it is thought that from a sufficiently large number of perceptual facts we can infer the character of the thing-in-itself which lies behind these facts. Formerly it was from concepts, now it is from percepts, that the Realist seeks to evolve the metaphysically real. Because concepts are before the mind in transparent clearness, it was thought that we might deduce from them the metaphysically real with absolute certainty. Percepts are not given with the same transparent clearness. Each fresh one is a little different from others of the same kind which preceded it. In principle, therefore, anything inferred from past experience is somewhat modified by each subsequent experience. The character of the metaphysically real thus obtained can therefore be only relatively true, for it is open to correction by further instances. The character of Von Hartmann's Metaphysics depends on this methodological principle. The motto on the title-page of his first important book is, "Speculative results gained by the inductive method of Science." The form which the Metaphysical Realist at the present day gives to his things-in-themselves is obtained by inductive inferences. Consideration of the process of knowledge has convinced him of the existence of an objectively-real world-nexus, over and above the subjective world which we know by means of percepts and concepts. The nature of this reality he thinks he can determine by inductive inferences from his percepts. ADDITION TO THE REVISED EDITION (1918).