The Subjective Materialist Doctrine of Protagoras

Anaxagoras, Democritus, Protogoras, and Empedocles held their opinions because they they thought, ’that which is’ was identical with the sensible world.

But physicality has largely the nature of the indeterminate.

Therefore, they speak plausibly.

But they do not say what is true.

They saw that this world is in movement and changes, from which no true absolute statement can be made.

So they said that:

• everything is changing
• yet nothing could truly be affirmed

Cratylus, a Heraclitean, held the most extreme of this belief.

• He criticized Heraclitus for saying that it is impossible to step twice into the same river.
• He believed that you cannot even step into a river once.

I understand why they say that the changing does not exist when it is changing.

But this is disputable.

This is because:

• that which is losing a quality had that quality which is merely being lost
• that which is gaining a quality already has a scope for that quality.

A thing that perishes means it has existed.

A thing that is coming to be, means it has a cause.

These processes cannot go on ad infinitum.

It is not the same thing to change in quantity and in quality.

In a change in quantity, the thing is not constant.

Yet it still keeps its form which lets us know each thing.

The view of the Heraclitean is wrong as they assert for the whole material universe what they saw only in a minority of sensible things.

This is because only that region of the sensible world which immediately surrounds us is always in the process of destruction and generation.

But this is region is not even a fraction of the whole.

So it would have been juster to acquit this part of the world than to condemn the other part.

We must show them that there is something whose nature is changeless.

Those people who say that things are at the same time physical and abstract.

• This means that all things are at rest instead of movement because there is nothing into which they can change since all attributes belong already to all subjects.

Not everything which appears is true.

This is because physical appearance is different from sensation.

Our opponents ask whether magnitudes are as great,

and colours are the same when near and far or when seen by the healthy and the sick.

and weight is heavy to the weak and to the strong.

Obviously, they do not think these to be open questions; no one, at least, if when he is in Libya he has fancied one night that he is in Athens, starts for the concert hall.

And again with regard to the future, as Plato says, surely the opinion of the physician and that of the ignorant man are not equally weighty, for instance, on the question whether a man will get well or not.-And again, among sensations themselves the sensation of a foreign object and that of the appropriate object, or that of a kindred object and that of the object of the sense in question, are not equally authoritative, but in the case of colour sight, not taste, has the authority, and in the case of flavour taste, not sight; each of which senses never says at the same time of the same object that it simultaneously is ‘so and not so’.

But not even at different times does one sense disagree about the quality, but only about that to which the quality belongs. I mean, for instance, that the same wine might seem, if either it or one’s body changed, at one time sweet and at another time not sweet; but at least the sweet, such as it is when it exists, has never yet changed, but one is always right about it, and that which is to be sweet is of necessity of such and such a nature. Yet all these views destroy this necessity, leaving nothing to be of necessity, as they leave no essence of anything; for the necessary cannot be in this way and also in that, so that if anything is of necessity, it will not be ‘both so and not so’.

If only the sensible exists, there would be nothing if animate things were not; for there would be no faculty of sense.

Now the view that neither the sensible qualities nor the sensations would exist is doubtless true (for they are affections of the perceiver), but that the substrata which cause the sensation should not exist even apart from sensation is impossible.

For sensation is surely not the sensation of itself, but there is something beyond the sensation, which must be prior to the sensation; for that which moves is prior in nature to that which is moved, and if they are correlative terms, this is no less the case.