The Lives and Opinions of Eminent Philosophers by Diogenes Laërtius (best free ebook reader txt) 📕

also affirm that there are no such things as signs; for if there are signs, they argue they must be such as are apprehended either by the senses or by the intellect. Now, there are none which are apprehended by the senses, for everything which is apprehended by the senses is general, while a sign is something particular. Moreover, any object which is apprehended by the senses has an existence of its own, while signs are only relative. Again, signs are not apprehended by the intellect, for in that case they would be either the visible manifestation of a visible thing, or the invisible manifestation of an invisible thing, or the invisible sign of a visible thing, or the visible sign of an invisible thing. But none of all these cases are possible; there are therefore no such things as signs at all.

There is therefore no such thing as a visible sign of a visible thing; for that which is visible has no need of a sign. Nor, again, is there any invisible sign of an invisible thing; for when anything is manifested by means of another thing, it must become visible. On the same principle there is no invisible sign of a visible object; for that which aids in the perception of something else must be visible. Lastly, there is no visible manifestation of an invisible thing; for as a sign is something wholly relative, it must be perceived in that of which it is the sign; and that is not the case. It follows, therefore, that none of those things which are not visible in themselves admit of being perceived; for one considers signs as things which aid in the perception of that which is not evident by itself.

They also wholly discard, and, as far as depends on them, overturn the idea of any cause, by means of this same train of reasoning. Cause is something relative. It is relative to that of which it is the cause. But that which is relative is only conceived, and has no real existence. The idea of a cause then is a pure conception; for, inasmuch as it is a cause, it must be a cause of something; otherwise it would be no cause at all. In the same way as a father cannot be a father, unless there exists some being in respect of whom one gives him the title of father; so too a cause stands on the same ground. For, supposing that nothing exists relatively to which a cause can be spoken of; then, as there is no production, or destruction, or anything of that sort, there can likewise be no cause. However, let us admit that there are such things as causes. In that case then, either a body must be the cause of a body, or that which is incorporeal must be the cause of that which is incorporeal. Now neither of these cases is possible, therefore, there is no such thing as cause. In fact, one body cannot be the cause of another body, since both bodies must have the same nature; and if it be said that one is the cause, inasmuch as it is a body, then the other must be a cause for the same reason. And in that case one would have two reciprocal causes; two agents without any passive subject.

Again, one incorporeal thing cannot be the cause of another incorporeal thing for the same reason. Also, an incorporeal thing cannot be the cause of a body, because nothing that is incorporeal can produce a body. Nor, on the other hand, can a body be the cause of anything incorporeal, because in every production there must be some passive subject matter; but, as what is incorporeal is by its own nature protected from being a passive subject, it cannot be the object of any productive power. There is, therefore, no such thing as any cause at all. From all which it follows that the first principles of all things have no reality; for such a principle, if it did exist, must be both the agent and the efficient cause.

Again, there is no such thing as motion. For whatever is moved, is moved either in the place in which it is, or in that in which it is not. It certainly is not moved in the place in which it is, and it is impossible that it should be moved in the place in which it is not; therefore, there is no such thing as motion at all.

They also denied the existence of all learning. If, said they, anything is taught, then either that which does exist is taught in its existence or that which does not exist is taught in its nonexistence; but that which does exist is not taught in its existence (for the nature of all existent things is visible to all men, and is known by all men); nor is that which does not exist taught in its nonexistence, for nothing can happen to that which does not exist, so that to be taught cannot happen to it.

Nor again, say they, is there any such thing as production. For that which is, is not produced, for it exists already; nor that which is not, for that does not exist at all. And that which has no being nor existence at all, cannot be produced.

Another of their doctrines is that there is no such thing as any natural good or natural evil. For if there be any natural good or natural evil, then it must be good to everyone or evil to everyone; just as snow is cold to everyone. But there is no such thing as one general good or evil which is common to all beings; therefore, there is no such thing as any natural good or natural evil. For either one must pronounce everything good which is thought so by anyone whatever, or one must say that it does not follow that everything which is thought