On the nature of things (books 4 - 6)   

Yet if, percase, thou deemest that ere this
Existed all things even the same, but that
Perished the cycles of the human race
In fiery exhalations, or cities fell
By some tremendous quaking of the world,
Or rivers in fury, after constant rains,
Had plunged forth across the lands of earth
And whelmed the towns- then, all the more must thou
Confess, defeated by the argument,
That there shall be annihilation too
Of lands and sky. For at a time when things
Were being taxed by maladies so great,
And so great perils, if some cause more fell
Had then assailed them, far and wide they would
Have gone to disaster and supreme collapse.
And by no other reasoning are we
Seen to be mortal, save that all of us
Sicken in turn with those same maladies
With which have sickened in the past those men
Whom Nature hath removed from life.
Again,
Whatever abides eternal must indeed
Either repel all strokes, because 'tis made
Of solid body, and permit no entrance
Of aught with power to sunder from within
The parts compact- as are those seeds of stuff
Whose nature we've exhibited before;
Or else be able to endure through time
For this: because they are from blows exempt,
As is the void, the which abides untouched,
Unsmit by any stroke; or else because
There is no room around, whereto things can,
As 'twere, depart in dissolution all-
Even as the sum of sums eternal is,
Without or place beyond whereto things may
Asunder fly, or bodies which can smite,
And thus dissolve them by the blows of might.
But not of solid body, as I've shown,
Exists the nature of the world, because
In things is intermingled there a void;
Nor is the world yet as the void, nor are,
Moreover, bodies lacking which, percase,
Rising from out the infinite, can fell
With fury-whirlwinds all this sum of things,
Or bring upon them other cataclysm
Of peril strange; and yonder, too, abides
The infinite space and the profound abyss-
Whereinto, lo, the ramparts of the world
Can yet be shivered. Or some other power
Can pound upon them till they perish all.
Thus is the door of doom, O nowise barred
Against the sky, against the sun and earth
And deep-sea waters, but wide open stands
And gloats upon them, monstrous and agape.
Wherefore, again, 'tis needful to confess
That these same things are born in time; for things
Which are of mortal body could indeed
Never from infinite past until to-day
Have spurned the multitudinous assaults
Of the immeasurable aeons old.

Again, since battle so fiercely one with other
The four most mighty members the world,
Aroused in an all unholy war,