Finally, however, there is some ground for thinking Sigwart would say: what exists is that which can be perceived or can be inferred as perceivable, for he adds: “hence (on account of this causal relation) from what is _perceivable_ also an existence which is merely _inferred_ may be asserted.” That all this is equally to be rejected it is not difficult to recognize. For (1) To “infer” the existence of something does not mean so much as “to infer that it is capable of being perceived.” If, for example, the existence of atoms and of empty spaces could be assured by inference, we should still be very far from proving their perceptibility either to ourselves or to some other being. If any one were to conclude the existence of God while giving up the attempt “to give vividness” to the thought by anthropomorphic means, he would not on this account believe that God must be perceptible to one of his creatures or even that he is the object of his own perception. 2. From this point of view it would be absurd for any one to say: “I am convinced that there is much the existence of which can neither be perceived at any time or even inferred by anybody.” For that would mean: “I am convinced that much can be perceived or can be inferred to be capable of perception which yet can never be perceived or inferred.” Who does not recognize here how far Sigwart has strayed from the true notion of existence! 3. Should Sigwart wish in this passage to widen the notion of existence to such a degree as to think that existence is that which can either be perceived or inferred from some perceivable object, or again, stands in some sort of causal relation to what is perceivable, it might be replied--if indeed such a monstrous notion of existence still require refutation--that even this notion is still too narrow. If, for example, I say: It may be that an empty space exists but this can never with certainty be known by any one, I thereby confess that existence may perhaps belong to empty space; but I deny most definitely that it is perceptible, or that it is to be inferred from that which is perceptible. In regard to relations of cause and effect on the other hand, it is of course impossible that empty space (which is certainly no thing) can stand in such a relation to anything perceivable. We should thus once again arrive at an absurd meaning in interpretation of an assertion in no way absurd.