The idea of a thing in itself independent of space and time and the unknowableness of the thing in itself are the basis of all agnosticism. And an agnostic tendency is at present predominant even among positive workers and thinkers. Agnosticism is still the philosophy of the day even among those who have surrendered its basis (which is Kant’s transcendental idealism) and accept the monistic world-conception. Friedrich Jodl, professor at the University of Prague and author of the well-known “History of Ethics,” in answer to a letter of mine formulates in concise terms this modernised view of a thing in itself. He writes: “You are right. The thing in itself is a dangerous idea,—one that easily leads astray. But so long as we have no better expression to represent the relation for which it stands we shall have to use it. You also accept the following three momenta: (1) Objective existence or reality. (2) Effectiveness of Reality upon consciousness, i. e. sensation. (3) Effectiveness of sensation upon consciousness and reproduction of sensation in consciousness, i. e. representation. Nobody, however, can maintain that in sensation, and still less in representation, the whole of reality will appear in consciousness. First we learn from history what progress has been made in the cognition of reality and secondly it is obvious that we are infinitely far from an actual comprehension of reality. We have strong reasons to suspect that there are many processes in reality which in no way affect our sensibility and cannot enter into consciousness, and we know for sure that we do not comprehend—i. e. reconstruct from them assumed causes—many things, indeed most things, which we observe in their effects. Our cognition of nature, if we begin to construct, always leads us to some _x_. It may be doubted whether this _x_ is an unknown or an unknowable. In my opinion it is both—anyhow we cannot eliminate it. “I am convinced that many things which are unknown to-day and appear as unknowable will be known and knowable in a thousand years. But I doubt whether the total mass of the Unknowable has been noticeably diminished. For the Unknowable is infinite and the infinite if divided by any finite number can never produce a finite number. Every solved problem contains new and greater problems. What shall we call this? I believe that the term “thing in itself” is after all the best expression. Whoever wants to turn a mystic on account of it cannot be prevented. This state of things can be brought out of existence by an act of violence only.”