the comprehension of the causes of things: it is the
discernment of a true idea, by distinguishing it from other
perceptions, and by investigating its nature, in order that
we may so train our mind that it may, by a given standard,
comprehend whatsoever is intelligible, by laying down
certain rules as aids, and by avoiding useless mental
exertion.

[38] (1) Whence we may gather that method is nothing else
than reflective knowledge, or the idea of an idea; and that
as there can be no idea of an idea - unless an idea exists
previously, - there can be no method without a pre-existent
idea. (2) Therefore, that will be a good method which
shows us how the mind should be directed, according to the
standard of the given true idea.
(38:3) Again, seeing that the ratio existing between two
ideas the same as the ratio between the actual realities
corresponding to those ideas, it follows that the reflective
knowledge which has for its object the most perfect being is
more excellent than reflective knowledge concerning other
objects - in other words, that method will be most perfect
which affords the standard of the given idea of the most
perfect being whereby we may direct our mind.

[39] (1) We thus easily understand how, in proportion as it
acquires new ideas, the mind simultaneously acquires fresh
instruments for pursuing its inquiries further. (2) For we
may gather from what has been said, that a true idea must
necessarily first of all exist in us as a natural instrument;
and that when this idea is apprehended by the mind, it enables