Vitae philosophorum

Therefore it is impossible to pronounce judgement on opinions about sensibles or intelligibles; and if the conflict in our thoughts compels us to disbelieve every one, the standard or measure, by which it is held that all things are exactly determined, will be destroyed, and we must deem every statement of equal value. Further, say they, our partner in an inquiry into a phenomenon is either to be trusted or not. If he is, he will have nothing to reply to the man to whom it appears to be the opposite[*](e.g. to be not a serpent, but a coil of rope.); for just as our friend who describes what appears to him is to be trusted, so is his opponent. If he is not to be trusted, he will actually be disbelieved when he describes what appears to him.

We must not assume that what convinces us is actually true. For the same thing does not convince every one, nor even the same people always. Persuasiveness sometimes depends on external circumstances, on the reputation of the speaker,

on his ability as a thinker or his artfulness, on the familiarity or the pleasantness of the topic.

Again, they would destroy the criterion by reasoning of this kind. Even the criterion has either been critically determined or not. If it has not, it is definitely untrustworthy, and in its purpose of distinguishing is no more true than false. If it has, it will belong to the class of particular judgements, so that one and the same thing determines and is determined, and the criterion which has determined will have to be determined by another, that other by another, and so on ad infinitum.

In addition to this there is disagreement as to the criterion, some holding that man is the criterion, while for some it is the senses, for others reason, for others the apprehensive presentation. Now man disagrees with man and with himself, as is shown by differences of laws and customs. The senses deceive, and reason says different things. Finally, the apprehensive presentation is judged by the mind, and the mind itself changes in various ways. Hence the criterion is unknowable, and consequently truth also.

They deny, too, that there is such a thing as a sign. If there is, they say, it must either be sensible or intelligible. Now it is not sensible, because what is sensible is a common attribute, whereas a sign is a particular thing. Again, the sensible is one of the things which exist by way of difference, while the sign belongs to the category of relative. Nor is a sign an object of thought, for objects of thought are of four kinds, apparent judgements on things apparent, non-apparent judgements on things nonapparent, non-apparent on apparent, or apparent on non-apparent; and a sign is none of these, so

nor, lastly, is it apparent on non-apparent, because the sign, being relative, must be apprehended along with that of which it is the sign, which is not here the case. It follows that nothing uncertain can be apprehended; for it is through signs that uncertain things are said to be apprehended.[*](This conclusion would debar us from all extension of knowledge beyond what is apparent here and now; whereas the dogmatists permit us from such facts to advance to what is not immediately evident, the realm of the unknown or as yet unascertained (ἄδηλον).).

Causes, too, they destroy in this way. A cause is something relative; for it is relative to what can be caused, namely, the effect. But things which are relative are merely objects of thought and have no substantial existence.

Therefore a cause can only be an object of thought; inasmuch as, if it be a cause, it must bring with it that of which it is said to be the cause, otherwise it will not be a cause. Just as a father, in the absence of that in relation to which he is called father, will not be a father, so too with a cause. But that in relation to which the cause is thought of, namely the effect, is not present; for there is no coming into being or passing away or any other process: therefore there is no such thing as cause. Furthermore, if there is a cause, either bodies are the cause of bodies, or things incorporeal of things incorporeal; but neither is the case; therefore there is no such thing as cause. Body in fact could not be the cause of body, inasmuch as both have the same nature. And if either is

But if both be alike causes, there will be nothing to be acted upon Nor can an incorporeal thing be the cause of an incorporeal thing, for the same reason. And a thing incorporeal cannot be the cause of a body, since nothing incorporeal creates anything corporeal. And, lastly, a body cannot be the cause of anything incorporeal, because what is produced must be of the material operated upon; but if it is not operated upon because it is incorporeal, it cannot be produced by anything whatever. Therefore there is no such thing as a cause. A corollary to this is their statement that the first principles of the universe have no real existence; for in that case something must have been there to create and act.

Furthermore there is no motion; for that which moves moves either in the place where it is or in a place where it is not. But it cannot move in the place where it is, still less in any place where it is not. Therefore there is no such thing as motion.

They used also to deny the possibility of learning. If anything is taught, they say, either the existent is taught through its existence or the non-existent through its non-existence. But the existent is not taught through its existence, for the nature of existing things is apparent to and recognized by all; nor is the non-existent taught through the nonexistent, for with the non-existent nothing is ever done, so that it cannot be taught to anyone.

Nor, say they, is there any coming into being. For that which is does not come into being, since it is; nor yet that which is not, for it has no substantial