XVIII. First of all I reply, that you are bringing me to the arguments of Democritus, with whom I do not agree. And I will the more readily refute them, on account of that doctrine which is laid down very clearly by the more refined natural philosophers, that everything has its own separate property. For grant that those ancient Servilii who were twins were as much alike as they are said to have been, do you think that that would have made them the same? They were not distinguished from one another out of doors, but they were at home. They were not distinguished from one another by strangers, but they were by their own family. Do we not see that this is frequently the case, that those people whom we should never have expected to be able to know from one another, we do by practice distinguish so easily that they do not appear to be even in the least alike? Here, however, you may struggle; I will not oppose you. Moreover, I will grant that that very wise man who is the subject of all this discussion, when things like one another come under his notice, in which he has not remarked any special character, will withhold his assent, and will never agree to any perception which is not of such a character as a false perception can never assume. But with respect to all other things he has a certain art by which he can distinguish what is true from what is false; and with respect to those similitudes he must apply the test of experience. As a mother distinguishes between twins by the constant practice of her eyes, so you too will distinguish when you have become accustomed to it. Do you not see that it has become a perfect proverb that one egg is like another? and yet we are told that at Delos (when it was a flourishing island) there were many people who used to keep large numbers of hens for the sake of profit; and that they, when they had looked upon an egg, could tell which hen had laid it. Nor does that fact make against our argument; for it is sufficient for us to be able to distinguish between the eggs. For it is impossible for one to assent to the proposition that this thing is that thing more, than by admitting that there is actually no difference at all between the two. For I have laid it down as a rule, to consider all perceptions true which are of such a character as those which are false cannot be. And from this I may not depart one finger’s breadth, as they say, lest I should throw everything into confusion. For not only the knowledge of what is true and false, but their whole nature too, will be destroyed if there is no difference between one and the other. And that must be very absurd which you sometimes are in the habit of saying, when perceptions are imprinted on the mind, that what you say is, not that there is no difference between the impressions, but only that there is none between certain appearances and forms which they assume. As if perceptions were not judged of by their