The Basis of the Truth

Protagoras said that man is the measure of all things. It means:

• that which seems to each man is also is.
• that the same thing both is and is not, and is bad and good
• that the contents of all other opposite statements are true, because often a particular thing appears beautiful to some and the contrary of beautiful to others, and that which appears to each man is the measure.

This opinion arose from:

• the doctrine of the natural philosophers, and
• the fact that all men have not the same views about the same things

Natural philosophers have a dogma that nothing comes from nothing, something comes from something.

This means that white can only exist if:

• white did not exist before, and
• non-white existed before.

This is because something that becomes white must come from that which is not white. Thus, it comes ’to be’ out of that which is not unless the same thing was at the beginning white and not-white.

We solve this by saying:

• in what sense things that come to be come to be from that which is not, and
• in what sense from that which is.

But to attend to the fancies of disputing parties is childish, since one of them must be mistaken. This is true for sensation.

The same thing never appears sweet to some and the contrary of sweet to others, unless in the one case the sense-organ which discriminates the aforesaid flavours has been perverted and injured.

If this is so:

• the one party must be taken to be the measure, and
• the other must not.

This will apply for:

• good and bad
• beautiful and ugly
• etc.

For to maintain the view we are opposing is just like maintaining that the things that appear to people who put their finger under their eye and make the object appear two instead of one must be two (because they appear to be of that number) and again one (for to those who do not interfere with their eye the one object appears one).

It is absurd to base our judgement of the truths on the fact that the things of this earth change and never remain in the same state.

This is because when we pursue the truth, we must start from the things that are always in the same state and never change. Examples are the heavenly bodies. They do not appear to be now of one nature and again of another, but are manifestly always the same and share in no change.

If there is movement, there is also something moved, and everything is moved out of something and into something.

It follows that that that which is moved must first be in that out of which it is to be moved, and then not be in it, and move into the other and come to be in it, and that the contradictory statements are not true at the same time, as these thinkers assert they are.

If the things of this earth continuously flow and move in respect of quantity-if one were to suppose this, although it is not true-why should they not endure in respect of quality?

For the assertion of contradictory statements about the same thing seems to have arisen largely from the belief that the quantity of bodies does not endure, which, our opponents hold, justifies them in saying that the same thing both is and is not four cubits long. But essence depends on quality, and this is of determinate nature, though quantity is of indeterminate.

When the doctor orders people to take some particular food, why do they take it? In what respect is ’this is bread’ truer than ’this is not bread'?

And so it would make no difference whether one ate or not. But as a matter of fact they take the food which is ordered, assuming that they know the truth about it and that it is bread. Yet they should not, if there were no fixed constant nature in sensible things, but all natures moved and flowed for ever.

“Again, if we are always changing and never remain the same, what wonder is it if to us, as to the sick, things never appear the same? (For to them also, because they are not in the same condition as when they were well, sensible qualities do not appear alike; yet, for all that, the sensible things themselves need not share in any change, though they produce different, and not identical, sensations in the sick. And the same must surely happen to the healthy if the afore-said change takes place.) But if we do not change but remain the same, there will be something that endures.

The difficulties suggested by reasoning are not easy to solve unless they will posit something and no longer demand a reason for it. For it is only thus that all reasoning and all proof is accomplished; if they posit nothing, they destroy discussion and all reasoning.

Therefore with such men there is no reasoning. But as for those who are perplexed by the traditional difficulties, it is easy to meet them and to dissipate the causes of their perplexity. This is evident from what has been said.

Thus contradictory statements cannot be truly made about the same subject at one time, nor can contrary statements, because every contrariety depends on privation. This is evident if we reduce the definitions of contraries to their principle.

“Similarly, no intermediate between contraries can be predicated of one and the same subject, of which one of the contraries is predicated. If the subject is white we shall be wrong in saying it is neither black nor white, for then it follows that it is and is not white; for the second of the two terms we have put together is true of it, and this is the contradictory of white.

It is wrong to accept the views of Heraclitus or Anaxagoras.

It would mean that contraries would be predicated of the same subject. When Anaxagoras says that in everything there is a part of everything, he says nothing is sweet any more than it is bitter, and so with any other pair of contraries, since in everything everything is present not potentially only, but actually and separately.

Similarly all statements cannot be false nor all true, both because of many other difficulties which might be adduced as arising from this position, and because if all are false it will not be true to say even this, and if all are true it will not be false to say all are false.