On the nature of things (books 1 - 3)   

What honoured sage, Democritus, lays down-
That proposition, that primordials
Of body and mind, each super-posed on each,
Vary alternately and interweave
The fabric of our members. For not only
Are the soul-elements smaller far than those
Which this our body and inward parts compose,
But also are they in their number less,
And scattered sparsely through our frame. And thus
This canst thou guarantee: soul's primal germs
Maintain between them intervals as large
At least as are the smallest bodies, which,
When thrown against us, in our body rouse
Sense-bearing motions. Hence it comes that we
Sometimes don't feel alighting on our frames
The clinging dust, or chalk that settles soft;
Nor mists of night, nor spider's gossamer
We feel against us, when, upon our road,
Its net entangles us, nor on our head
The dropping of its withered garmentings;
Nor bird-feathers, nor vegetable down,
Flying about, so light they barely fall;
Nor feel the steps of every crawling thing,
Nor each of all those footprints on our skin
Of midges and the like. To that degree
Must many primal germs be stirred in us
Ere once the seeds of soul that through our frame
Are intermingled 'gin to feel that those
Primordials of the body have been strook,
And ere, in pounding with such gaps between,
They clash, combine and leap apart in turn.
But mind is more the keeper of the gates,
Hath more dominion over life than soul.
For without intellect and mind there's not
One part of soul can rest within our frame
Least part of time; companioning, it goes
With mind into the winds away, and leaves
The icy members in the cold of death.
But he whose mind and intellect abide
Himself abides in life. However much
The trunk be mangled, with the limbs lopped off,
The soul withdrawn and taken from the limbs,
Still lives the trunk and draws the vital air.
Even when deprived of all but all the soul,
Yet will it linger on and cleave to life,-
Just as the power of vision still is strong,
If but the pupil shall abide unharmed,
Even when the eye around it's sorely rent-
Provided only thou destroyest not
Wholly the ball, but, cutting round the pupil,
Leavest that pupil by itself behind-
For more would ruin sight. But if that centre,
That tiny part of eye, be eaten through,
Forthwith the vision fails and darkness comes,
Though in all else the unblemished ball be clear.
'Tis by like compact that the soul and mind
Are each to other bound forevermore.

THE SOUL IS MORTAL

Now come: that thou mayst able be to know
That minds and the light souls of all that live
Have mortal birth and death, I will go on
Verses to build meet for thy rule of life,