Book 10
1.48
Besides this, remember that the production of the images is as quick as thought. For particles are continually streaming off from the surface of bodies, though no diminution of the bodies is observed, because other particles take their place.If vision is to be not merely intermittent but continuous, images must be perpetually streaming from the objects seen to our eyes; there must be a continual succession of similar images. Cf. Fr. 282 (Us.); Lucr. ii. 67-76, iv. 143-167. And those given off for a long time retain the position and arrangement which their atoms had when they formed part of the solid bodies, although occasionally they are thrown into confusion. Sometimes such filmse.g. mirage and monstrous shapes of clouds: Lucr. iv. 129-142; Diod. iii. 56. are formed very rapidly in the air, because they need not have any solid content; and there are other modes in which they may be formed. For there is nothing in all this which is contradicted by sensation, if we in some sort look at the clear evidence of sense, to which we should also refer the continuity of particles in the objects external to ourselves.
