Aristotelian, that his most usual thesis was: "That the touchstone and
square of all solid imagination, and of all truth, was an absolute
conformity to Aristotle's doctrine; and that all besides was nothing but
inanity and chimera; for that he had seen all, and said all." A position,
that for having been a little too injuriously and broadly interpreted,
brought him once and long kept him in great danger of the Inquisition at
Rome.

Let him make him examine and thoroughly sift everything he reads, and
lodge nothing in his fancy upon simple authority and upon trust.
Aristotle's principles will then be no more principles to him, than those
of Epicurus and the Stoics: let this diversity of opinions be propounded
to, and laid before him; he will himself choose, if he be able; if not,
he will remain in doubt.

"Che non men the saver, dubbiar m' aggrata."

["I love to doubt, as well as to know."--Dante, Inferno, xi. 93]

for, if he embrace the opinions of Xenophon and Plato, by his own reason,
they will no more be theirs, but become his own. Who follows another,
follows nothing, finds nothing, nay, is inquisitive after nothing.

"Non sumus sub rege; sibi quisque se vindicet."

["We are under no king; let each vindicate himself."
--Seneca, Ep.,33]

Let him, at least, know that he knows. It will be necessary that he
imbibe their knowledge, not that he be corrupted with their precepts;