The 2 Kinds of Motion

CLEINIAS: But why is the word ’nature’ wrong?

ATHENIAN: Because those who use the word mean that nature is the first creative power.

But if the soul turns out to be the primeval element, and not fire or air, then in the truest sense and beyond other things the soul may be said to exist by nature; and this would be true if you proved that the soul is older than the body, but not otherwise.

Let us be on our guard lest this most deceptive argument with its youthful looks, beguiling us old men, give us the slip and make a laughing-stock of us. Who knows but we may be aiming at the greater, and fail of attaining the lesser?

Suppose that we 3 have to pass a rapid river.

I am the youngest and most experienced in rivers.

So I make the first attempt by myself leaving you in safety on the bank.

I examine whether the river is passable by older men like yourselves.

If it is safe, then I invite you to follow.

But if the river is impassable by you, then there will have been no danger to anybody but myself—would not that seem to be a very fair proposal?

The argument in prospect is likely to be too much for you, out of your depth and beyond your strength, and I should be afraid that the stream of my questions might create in you who are not in the habit of answering, giddiness and confusion of mind, and hence a feeling of unpleasantness and unsuitableness might arise. I think therefore that I had better first ask the questions and then answer them myself while you listen in safety;

in that way I can carry on the argument until I have completed the proof that the soul is prior to the body.

Someone says to me, ‘O Stranger, are all things at rest and nothing in motion, or is the exact opposite of this true, or are some things in motion and others at rest?’ To this I shall reply that some things are in motion and others at rest.

‘And do not things which move move in a place, and are not the things which are at rest at rest in a place?’ Certainly. ‘And some move or rest in one place and some in more places than one?’

You mean to say, we shall rejoin, that those things which rest at the centre move in one place, just as the circumference goes round of globes which are said to be at rest? ‘Yes.’ And we observe that, in the revolution, the motion which carries round the larger and the lesser circle at the same time is proportionally distributed to greater and smaller, and is greater and smaller in a certain proportion. Here is a wonder which might be thought an impossibility, that the same motion should impart swiftness and slowness in due proportion to larger and lesser circles. ‘Very true.’

When you speak of bodies moving in many places, you seem to me to mean those which move from one place to another, and sometimes have one centre of motion and sometimes more than one because they turn upon their axis; and whenever they meet anything, if it be stationary, they are divided by it; but if they get in the midst between bodies which are approaching and moving towards the same spot from opposite directions, they unite with them. ‘I admit the truth of what you are saying.’ Also when they unite they grow, and when they are divided they waste away—that is, supposing the constitution of each to remain, or if that fails, then there is a second reason of their dissolution. ‘And when are all things created and how?’ Clearly, they are created when the first principle receives increase and attains to the second dimension, and from this arrives at the one which is neighbour to this, and after reaching the third becomes perceptible to sense. Everything which is thus changing and moving is in process of generation; only when at rest has it real existence, but when passing into another state it is destroyed utterly.

There are 2 kinds of motion:

1. One is able to move other things, but not move itself

2. One can move itself and other things

This works through composition and decomposition, by increase and diminution and generation and destruction.

That which moves other, and is changed by other, to be the ninth, and that which changes itself and others, and is coincident with every action and every passion, and is the true principle of change and motion in all that is—that we shall be inclined to call the tenth.

Of these 10 motions, The motion which is able to move itself is the mightiest and most efficient.

According to the true order, the tenth motion was really the first in generation and power.

Then follows the second, which was strangely called by us as the ninth.

When one thing changes another, and that another, of such will there be any primary changing element?

How can a thing which is moved by another ever be the beginning of change? Impossible. But when the self-moved changes other, and that again other, and thus thousands upon tens of thousands of bodies are set in motion, must not the beginning of all this motion be the change of the self-moving principle?

If, as most of these philosophers have the audacity to affirm, all things were at rest in one mass, which of the above-mentioned principles of motion would first spring up among them?

CLEINIAS: Clearly the self-moving; for there could be no change in them arising out of any external cause; the change must first take place in themselves.

ATHENIAN: Then self-motion is:

• the origin of all motions.
• the first which arises among things at rest as well as among things in motion.
• the eldest and mightiest principle of change, and that which is changed by another and yet moves other is second.

If we were to see this power existing in any earthy, watery, or fiery substance, simple or compound—how should we describe it?

CLEINIAS: You mean to ask whether we should call such a self-moving power as life? I think yes we should.

ATHENIAN: When we see soul in anything, we say it is life.

What is the essence of life?

These are the 3. From these 3, 2 questions which may be raised about anything.

Sometimes a person may give the name and ask the definition; or he may give the definition and ask the name.

Number like some other things is capable of being divided into equal parts; when thus divided, number is named ’even,’ and the definition of the name ’even’ is ’number divisible into two equal parts’?

I mean, that when we are asked about the definition and give the name, or when we are asked about the name and give the definition—in either case, whether we give name or definition, we speak of the same thing, calling ’even’ the number which is divided into two equal parts.