Hiretas of Syracuse, as Theophrastus tells us, thinks that the sun, and moon, and stars, and all the heavenly bodies, in short, stand still; and that nothing in the world moves except the earth; and, as that turns and revolves on its own axis with the greatest rapidity, he thinks that everything is made to appear by it as if it were the heaven which is moved while the earth stands still. And, indeed, some people think that Plato, in the Timæus, asserts this, only rather obscurely. What is your opinion, Epicurus? Speak. Do you think that the sun is so small?—Do I? Do you yourselves think it so large? But all of you are ridiculed by him, and you in your turn mock him. Socrates, then, is free from this ridicule, and so is Ariston of Chios, who thinks that none of these matters can be known. But I return to the mind and body. Is it sufficiently known by us what is the nature of the sinews and of the veins? Do we comprehend what the mind is?—where it is?—or, in short, whether it exists at all, or whether, as Dicæarchus thinks, there is no such thing whatever? If there is such a thing, do we know whether it has three divisions, as Plato thought; those of reason, anger, and desire?—or whether it is single and uniform? If it is single and uniform, do we know whether it is fire, or breath, or blood?—or, as Xenocrates says, number without a body?—though, what sort of thing that is, is not very easy to understand. And whatever it is, do we know whether it is mortal or eternal? For many arguments are alleged on both sides.