Melissus applied the results of his analysis in an interesting way to the question already raised by his predecessors, of the trustworthiness of sensation. His argument is as follows: "If there were many real existences, to each of them the same reasonings must apply as I have already used with reference to the one existence. That is to say, if earth really exists, and water and air and iron and gold and fire and things living and things dead; and black and white, and all the various things whose reality men ordinarily assume,--if all these really exist, and our sight and our hearing give us _facts_, then each of these as {50} really existing must be what we concluded the one existence must be; among other things, each must be unchangeable, and can never become other than it really is. But assuming that sight and hearing and apprehension are true, we find the cold becoming hot and the hot becoming cold; the hard changes to soft, the soft to hard; the living thing dies; and from that which is not living, a living thing comes into being; in short, everything changes, and what now is in no way resembles what was. It follows therefore that we neither see nor apprehend realities. "In fact we cannot pay the slightest regard to experience without being landed in self-contradictions. We assume that there are all sorts of really existing things, having a permanence both of form and power, and yet we imagine these very things altering and changing according to what we from time to time see about them. If they were realities as we first perceived them, our sight must now be wrong. For if they were real, they could not change. Nothing can be stronger than reality. Whereas to suppose it changed, we must affirm that the real has ceased to be, and that that which was not has displaced it." To Melissus therefore, as to his predecessors, the world of sense was a world of illusion; the very first principles or assumptions of which, as of the truthfulness of the senses and the reality of the various objects which we see, are unthinkable and absurd. {51}