3. Diogenes Laertius, Lives of The Philosophers, 9.90, 9.94, 9.96-9.97, 9.99-9.101, 10.32 (3rd cent. CE - 3rd cent. CE)
| 9.94. 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. 9.96. 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 non-apparent, non-apparent on apparent, or apparent on non-apparent; and a sign is none of these, so that there is no such thing as a sign. A sign is not apparent on apparent, for what is apparent needs no sign; nor is it non-apparent on non-apparent, for what is revealed by something must needs appear; 9.97. nor is it non-apparent on apparent, for that which is to afford the means of apprehending something else must itself be apparent; 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.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. 9.99. 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. 9.100. 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 existence, and that which is neither substantial nor existent cannot have had the chance of coming into being either. 9.101. There is nothing good or bad by nature, for if there is anything good or bad by nature, it must be good or bad for all persons alike, just as snow is cold to all. But there is no good or bad which is such to all persons in common; therefore there is no such thing as good or bad by nature. For either all that is thought good by anyone whatever must be called good, or not all. Certainly all cannot be so called; since one and the same thing is thought good by one person and bad by another; for instance, Epicurus thought pleasure good and Antisthenes thought it bad; thus on our supposition it will follow that the same thing is both good and bad. But if we say that not all that anyone thinks good is good, we shall have to judge the different opinions; and this is impossible because of the equal validity of opposing arguments. Therefore the good by nature is unknowable. 10.32. Nor is there anything which can refute sensations or convict them of error: one sensation cannot convict another and kindred sensation, for they are equally valid; nor can one sensation refute another which is not kindred but heterogeneous, for the objects which the two senses judge are not the same; nor again can reason refute them, for reason is wholly dependent on sensation; nor can one sense refute another, since we pay equal heed to all. And the reality of separate perceptions guarantees the truth of our senses. But seeing and hearing are just as real as feeling pain. Hence it is from plain facts that we must start when we draw inferences about the unknown. For all our notions are derived from perceptions, either by actual contact or by analogy, or resemblance, or composition, with some slight aid from reasoning. And the objects presented to mad-men and to people in dreams are true, for they produce effects – i.e. movements in the mind – which that which is unreal never does. |
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