From ignorance of this truth, or, if there was any one to whom it
was known, from neglect of it, the majority of those who in these
later ages aspired to be philosophers, blindly followed Aristotle,
so that they frequently corrupted the sense of his writings, and
attributed to him various opinions which he would not recognise as
his own were he now to return to the world; and those who did not
follow him, among whom are to be found many of the greatest minds,
did yet not escape being imbued with his opinions in their youth, as
these form the staple of instruction in the schools; and thus their
minds were so preoccupied that they could not rise to the knowledge
of true principles. And though I hold all the philosophers in
esteem, and am unwilling to incur odium by my censure, I can adduce
a proof of my assertion, which I do not think any of them will
gainsay, which is, that they all laid down as a principle what they
did not perfectly know. For example, I know none of them who did not
suppose that there was gravity in terrestrial bodies; but although
experience shows us very clearly that bodies we call heavy descend
towards the center of the earth, we do not, therefore, know the
nature of gravity, that is, the cause or principle in virtue of
which bodies descend, and we must derive our knowledge of it from
some other source. The same may be said of a vacuum and atoms, of
heat and cold, of dryness and humidity, and of salt, sulphur, and
mercury, and the other things of this sort which some have adopted
as their principles. But no conclusion deduced from a principle
which is not clear can be evident, even although the deduction be
formally valid; and hence it follows that no reasonings based on
such principles could lead them to the certain knowledge of any one
thing, nor consequently advance them one step in the search after
wisdom. And if they did discover any truth, this was due to one or
other of the four means above mentioned. Notwithstanding this, I am