Lucretius, De Rerum Natura
William Ellery Leonard, Ed.

If haply our hand be set beneath one eye
And press below thereon, then to our gaze
Each object which we gaze on seems to be,
By some sensation twain- then twain the lights
Of lampions burgeoning in flowers of flame,
And twain the furniture in all the house,
Two-fold the visages of fellow-men,
And twain their bodies. And again, when sleep
Has bound our members down in slumber soft
And all the body lies in deep repose,
Yet then we seem to self to be awake
And move our members; and in night's blind gloom
We think to mark the daylight and the sun;
And, shut within a room, yet still we seem
To change our skies, our oceans, rivers, hills,
To cross the plains afoot, and hear new sounds,
Though still the austere silence of the night
Abides around us, and to speak replies,
Though voiceless. Other cases of the sort
Wondrously many do we see, which all
Seek, so to say, to injure faith in sense-
In vain, because the largest part of these
Deceives through mere opinions of the mind,
Which we do add ourselves, feigning to see
What by the senses are not seen at all.
For naught is harder than to separate
Plain facts from dubious, which the mind forthwith
Adds by itself.