tion by the limits of knowledge. Once we are certain that our objects are strictly ours, are but the framing of our sensations in our a priori forms, we are thenceforth confronted with the limiting notion called the thing-in-itself. The doubt, thence-forward ineradicable, of our power to pass this limit turns into certainty of our impotence to do so, when we find, as Kant shows us, that the attempt must cast reason into systematic contradictions.
Our knowledge, then, is confined strictly to the field of phenomena; to knowing, not what is, but only what exists relatively to us; and within this field it is further restricted to the tracing of mechanical causation. For, again by Kant’s showing, its highest category is action and reaction, and so all the terms conjoined by its synthesis must be extended objects of sense. Hence Du Bois-Reymond’s “limits of the knowledge of Nature” become the limits of all knowledge whatever. While, then, our philosophy thus falls into step with natural science, it indeed vindicates to materialism the entire province of Nature, but at the same time excludes materialism from explaining mind. Mind and Nature stand contrasted as subject and object; the object, as simply presentation to mind, requires mind as the ground of its existence, and so can never explain mind.
But the relativity of our knowledge, continues Lange with especial emphasis, reaches wider than
