On the nature of things (books 4 - 6)   

And thus the rest do perish one and all,
Save those for which the mind prepares itself.
Further, it doth prepare itself indeed,
And hopes to see what follows after each-
Hence this result. For hast thou not observed
How eyes, essaying to perceive the fine,
Will strain in preparation, otherwise
Unable sharply to perceive at all?
Yet know thou canst that, even in objects plain,
If thou attendest not, 'tis just the same
As if 'twere all the time removed and far.
What marvel, then, that mind doth lose the rest,
Save those to which 'thas given up itself?
So 'tis that we conjecture from small signs
Things wide and weighty, and involve ourselves
In snarls of self-deceit.

SOME VITAL FUNCTIONS

In these affairs
We crave that thou wilt passionately flee
The one offence, and anxiously wilt shun
The error of presuming the clear lights
Of eyes created were that we might see;
Or thighs and knees, aprop upon the feet,
Thuswise can bended be, that we might step
With goodly strides ahead; or forearms joined
Unto the sturdy uppers, or serving hands
On either side were given, that we might do
Life's own demands. All such interpretation
Is aft-for-fore with inverse reasoning,
Since naught is born in body so that we
May use the same, but birth engenders use:
No seeing ere the lights of eyes were born,
No speaking ere the tongue created was;
But origin of tongue came long before
Discourse of words, and ears created were
Much earlier than any sound was heard;
And all the members, so meseems, were there
Before they got their use: and therefore, they
Could not be gendered for the sake of use.
But contrariwise, contending in the fight
With hand to hand, and rending of the joints,
And fouling of the limbs with gore, was there,
O long before the gleaming spears ere flew;
And Nature prompted man to shun a wound,
Before the left arm by the aid of art
Opposed the shielding targe. And, verily,
Yielding the weary body to repose,
Far ancienter than cushions of soft beds,
And quenching thirst is earlier than cups.
These objects, therefore, which for use and life
Have been devised, can be conceived as found
For sake of using. But apart from such
Are all which first were born and afterwards
Gave knowledge of their own utility-
Chief in which sort we note the senses, limbs:
Wherefore, again, 'tis quite beyond thy power
To hold that these could thus have been create
For office of utility.
Likewise,
'Tis nothing strange that all the breathing creatures
Seek, even by nature of their frame, their food.
Yes, since I've taught thee that from off the things