to the product of the second and third: still they do not see the
adequate proportionality of the given numbers, or, if they do see it,
they see it not by virtue of Euclid's proposition, but intuitively,
without going through any process.

[25] (1) In order that from these modes of perception the best may
be selected, it is well that we should briefly enumerate the means
necessary for attaining our end.

I. (2) To have an exact knowledge of our nature which we desire to
perfect, and to know as much as is needful of nature in general.

II. To collect in this way the differences, the agreements, and the
oppositions of things.

III. To learn thus exactly how far they can or cannot be modified.

IV. To compare this result with the nature and power of man.
(4) We shall thus discern the highest degree of perfection
to which man is capable of attaining.

[26] (1) We shall then be in a position to see which mode of
perception we ought to choose. (2) As to the first mode, it is
evident that from hearsay our knowledge must always be uncertain,
and, moreover, can give us no insight into the essence of a thing,
as is manifest in our illustration; now one can only arrive at
knowledge of a thing through knowledge of its essence, as will
hereafter appear. (3) We may, therefore clearly conclude that
the certainty arising from hearsay cannot be scientific in its
character. (4) For simple hearsay cannot affect anyone whose