And now, if for a paragraph or two I may be even offensively abstruse, the conditions of our positive experience, of our actual knowledge, are such, and are commonly recognized to be such, that there must always be an unknown. Every working hypothesis [p.123] by implication points to an unknown. It is equally true, however, that the conditions of positive experience are such that there is no fixity to this unknown; and the unknown changes in consequence, both in possible content and in possible quality or value, with every change in knowledge. But _always_ an unknown which is _never_ the same unknown must mean something more than merely a yet-to-be-known; yes, it must mean even more than an infinitely, eternally remote yet-to-be-known, for its being always, or its being infinitely distant, simply makes it something besides positive knowledge actual or possible. It must mean something which, though not knowledge, is nevertheless in knowledge, now and always; something served by all knowledge but itself other than any knowledge; something, then, which exceeds or transcends whatever the formal enabling conditions of knowledge are capable of presenting, but is itself intimately and vitally involved in the presentation; or, once more, something which is not at all in the character of a separate unknowable thing or sphere of things, nor even of a separate part in the things known or knowable, but is in the character rather of an unknowability, perhaps in a sense a relative unknowability, belonging to the very things and to every part of the very things that are known or, let me say, inhering in the bare possibility of all knowledge. Must there not be a sense in which just that which makes knowledge possible is itself quite impossible to knowledge? Who makes a law must be superior to the law, or "legally supreme," and what makes knowledge possible can hardly be fully and directly an object [p.124] of knowledge. Given actual, positive knowledge, then, and there must always be not merely an unknown, but also an unknowable; an unknowable, however, that is in and of the knowledge, not in place or in character a thing by itself.