"৳ Lastly, if a person supposes a thing different from what it is; this is not a knowledge of the thing in question, but a false opinion of it, widely distant from the truth of science: if a thing were therefore to befal in such a way, that the event of it is neither necessary nor certain; how can any one foresee that it is to happen? For as what we really do know is free from all uncertainty, so what is comprehended by science cannot be otherwise than as comprehended: hence... true science cannot err, because every thing must precisely be what her eye perceives it to be."