On the nature of things (books 1 - 3)   

Sought after long, discovered with sweet toil.
But under one name I'd have thee yoke them both;
And when, for instance, I shall speak of soul,
Teaching the same to be but mortal, think
Thereby I'm speaking also of the mind-
Since both are one, a substance interjoined.

First, then, since I have taught how soul exists
A subtle fabric, of particles minute,
Made up from atoms smaller much than those
Of water's liquid damp, or fog, or smoke,
So in mobility it far excels,
More prone to move, though strook by lighter cause
Even moved by images of smoke or fog-
As where we view, when in our sleeps we're lulled,
The altars exhaling steam and smoke aloft-
For, beyond doubt, these apparitions come
To us from outward. Now, then, since thou seest,
Their liquids depart, their waters flow away,
When jars are shivered, and since fog and smoke
Depart into the winds away, believe
The soul no less is shed abroad and dies
More quickly far, more quickly is dissolved
Back to its primal bodies, when withdrawn
From out man's members it has gone away.
For, sure, if body (container of the same
Like as a jar), when shivered from some cause,
And rarefied by loss of blood from veins,
Cannot for longer hold the soul, how then
Thinkst thou it can be held by any air-
A stuff much rarer than our bodies be?

Besides we feel that mind to being comes
Along with body, with body grows and ages.
For just as children totter round about
With frames infirm and tender, so there follows
A weakling wisdom in their minds; and then,
Where years have ripened into robust powers,
Counsel is also greater, more increased
The power of mind; thereafter, where already
The body's shattered by master-powers of eld,
And fallen the frame with its enfeebled powers,
Thought hobbles, tongue wanders, and the mind gives way;
All fails, all's lacking at the selfsame time.
Therefore it suits that even the soul's dissolved,
Like smoke, into the lofty winds of air;
Since we behold the same to being come
Along with body and grow, and, as I've taught,
Crumble and crack, therewith outworn by eld.

Then, too, we see, that, just as body takes
Monstrous diseases and the dreadful pain,
So mind its bitter cares, the grief, the fear;
Wherefore it tallies that the mind no less
Partaker is of death; for pain and disease
Are both artificers of death,- as well
We've learned by the passing of many a man ere now.
Nay, too, in diseases of body, often the mind
Wanders afield; for 'tis beside itself,
And crazed it speaks, or many a time it sinks,
With eyelids closing and a drooping nod,
In heavy drowse, on to eternal sleep;
From whence nor hears it any voices more,
Nor able is to know the faces here