Trust Your Senses

Lucretius, On the Nature of Things 1.699-700 (tr. W.H.D. Rouse, rev. Martin F. Smith):

For to what shall we appeal? What can we find more certain than the senses themselves, to mark for us truth and falsehood?

quo referemus enim? quid nobis certius ipsis
sensibus esse potest, qui vera ac falsa notemus?

700 qui = quo, referring back to quid.

Related post: Believing One's Own Eyes.