The Eyes Cannot Know The Nature

From Book IV of De Rerum Natura, in Lucretius's extensive treatment of optical illusions and the limits of sensory perception. His point is not that the eyes lie but that they provide raw data that the mind must interpret correctly: an oar half-submerged in water looks bent, but the eye is doing its job — the fault lies in drawing the wrong inference. This was the Epicurean response to Sceptics who used perceptual illusions to deny the reliability of the senses altogether: illusions don't undermine all perception; they show that perception must be supplemented by rational analysis.