Dogmatic Realism, of which Leibnitz and, at a later date, Herbart are the most important representatives in modern philosophy, on the contrary, while maintaining that real being is independent of experience, at the same time holds that it is possible to have positive knowledge not only of its existence but of its nature. In principle, both these forms of Realism have been already excluded by the argument of Book I. chap. 2, § 4. The supreme importance of the principle on which the argument rests may perhaps warrant us in once more briefly recurring to it. Our reasoning, it will be remembered, took the form of a challenge. Produce any instance you please, we said to the realist, whom we had not then learned to know by that name, of what you personally regard as reality, and we will undertake to show that it derives its reality for you from the very fact that it is not ultimately separable from the experience of a subject. A thing is real for you, and not merely imaginary, precisely because in some aspect of its character it enters into and affects your own experience. Or, what is the same thing in other words, it is real for you because it affects favourably or otherwise some subjective interest of your own. To be sure, the thing as it enters into your experience, as it affects your own subjective interests, is not the thing as it is in its fulness; it only touches your life through some one of its many sides. And this may lead you to argue that the real thing is the unexperienced “condition” of a modification of your experience. But then we had again to ask what you mean by saying that facts which you do not experience are real as “conditions” of what you do experience. And we saw that the only meaning we could attach to the reality of the “condition” was presence to an experience which transcends your own. To this general argument we may add two corollaries or supplementary considerations, which, without introducing anything fresh, may help to make its full force more apparent.