On the Nature of the Universe (Oxford World’s Classics) (15 page)

Driven by unseen blows from them; and they

Attack in turn bodies a little larger.

The movement thus ascends from primal atoms

And comes out gradually up to our senses,

And thus it is that those bodies also move

That we can see in sunbeams, though the blows

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That make them do it are invisible.

Now, as to the speed with which the atoms move.

This in a few words you may understand,

Good Memmius, from what I now shall tell you.

First, when dawn strews new light across the earth,

And the birds flying through the pathless woods

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In the soft air fill with their liquid notes,

So varied and so sweet, the place below,

We see then plain and manifest to all

How suddenly the rising sun is wont

To clothe the world and flood it with his light.

But that heat and light serene the sun sends forth

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Do not pass through empty void; and for this reason

They are compelled to go more slowly, and

To cleave their way as it were through waves of air.

Nor do the particles of heat move separately,

But in a mass all linked and massed together,

So that at the same time they drag each other back

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And meet external obstacles, and so move more slowly.

But atoms, which are completely solid and single,

When they pass through the empty void, and nothing

Outside of them delays them, then they move

As single units on the course on which they started.

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Therefore they must be of surpassing speed

And move much faster than the light of the sun,

And cover a distance many times as great

In the time the sun’s flash takes to cross the sky.

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And not to follow every single atom

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To see in what way everything is done.

Some people oppose this, being ignorant of matter,

Believing that without the power of gods

Nature could never match the needs of men

So fitly as she does, so very closely,

Changing the seasons and producing crops,

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And all those other things which pleasure divine,

The guide of life, leads mortals to enjoy,

And through the arts of Venus coaxes them

To breed, and propagate the generations,

Lest the human race should perish. But when they imagine

That gods have ordered all things for men’s sake,

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In every way they have fallen far from truth.

For even if I had no knowledge of atoms,

This from the order of the heavens itself

And many other facts I would dare assert—

That in no way for us the power of gods

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Fashioned the world and brought it into being.

So great the faults of which it stands possessed.

This, Memmius, I will make clear to you later.

Now I’ll complete my account of the motion of atoms.

This is the place, I think, to make the point

That no material thing can by its own power

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Ever be lifted up, or travel upwards.

Do not let the atoms that make flame deceive you.

For trees and shining crops spring into birth

Upwards and grow and make their increase upwards,

Though all weights by themselves tend downwards.

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And when fires leap up to the roofs of houses

And with swift flame devour beams and timbers,

We must not think that of their own accord

They do this, without some force below to drive them.

Blood in the same way, let out from our bodies,

Spurts in a jet aloft and splashes gore.

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Do you not see also the power with which water

Spits out beams and timbers? We press them down,

Deep down, many of us pushing all together

With might and main, and the harder we push them down

The more the water wants to spew them up,

And throw them back again, so that more than half

Emerges and shoots up above the surface.

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And yet I think we have no doubt that all of them

Left to themselves would move downwards through the void.

The same thing must happen with flames. These under pressure

Can shoot up into the air, although their weights,

Left to themselves, must fight to drag them down.

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And the nocturnal torches of the sky

Flying aloft, you see how in their wake

Long trails of flame they draw, wherever nature

Has set them on their course across the heavens.

And see how stars and meteors fall to earth.

And the sun also from the height of heaven

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Throws its heat out and sows the fields with light.

So the sun’s heat also inclines towards the earth.

Lightning you see through rainstorms flies aslant;

Now here, now there, the fires burst through the clouds

Headlong together; the flaming bolt falls to the earth.

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Now here is another thing I want you to understand.

While atoms move by their own weight straight down

Through the empty void, at quite uncertain times

And uncertain places they swerve slightly from their course.

You might call it no more than a mere change of motion.

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If this did not occur, then all of them

Would fall like drops of rain down through the void.

There would be no collisions, no impacts

Of atoms upon atom, so that nature

Would never have created anything.

If anyone believes that heavier atoms

Moving straight down more quickly through the void

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Can fall on lighter atoms from above

And by this means produce the varied impacts

That can give rise to generative motions,

He is lost, and strays far from the path of truth.

For when things fall through water or thin air,

They must gain speed according to their weights;

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For water’s mass and air’s thin nature cannot

Slow down the pace of all things equally

But must give way more quickly to the heavier.

But, by contrast, nowhere at any time

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Can empty void make resistance to anything,

But as its nature demands it must give way.

Therefore through the calm and quiet void

All things must travel at an equal speed

Though with unequal weight. The heavier

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Will never have the power to fall upon

The lighter from above, nor by themselves

Beget impacts that make the varied mix

Of movements by which nature fashions things.

Therefore again and again I say that atoms must

Swerve slightly, just the very least—no more—

Or we shall find ourselves imagining

A sideways movement, which the facts refute.

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For it is plain and manifest that weights

When falling from above, left to themselves,

So far as meets the eye cannot move sideways.

But whose eye can perceive that nothing swerves

Ever so slightly from its straight course down?

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Again, if movement always is connected,

New motions coming from old in order fixed,

If atoms never swerve and make beginning

Of motions that can break the bonds of fate,

And foil the infinite chain of cause and effect,

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What is the origin of this free will

Possessed by living creatures throughout the earth?

Whence comes, I say, this will-power wrested from the fates

Whereby we each proceed where pleasure leads,

Swerving our course at no fixed time or place

But where the bidding of our hearts directs?

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For beyond doubt the power of the will

Originates these things and gives them birth

And from the will movements flow through the limbs.

Consider racehorses. The starting gates

Fly open, the horses are strong and keen to go,

But can’t break out as fast as their minds would wish.

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For all the mass of matter must be stirred

Through the whole body, roused through every limb,

Before it can follow the prompting of the mind.

So you may see that heart begins the motion

Then mind and will join in and drive it on

Until it reaches all the body and limbs.

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