happens, I have been forced so to arrange my proceedings, that we
may acquire by reflection and forethought what we cannot acquire
by chance, and that it may at the same time appear that, for
proving the truth, and for valid reasoning, we need no other means
than the truth and valid reasoning themselves: for by valid
reasoning I have established valid reasoning, and, in like measure,
I seek still to establish it.

[45] (1) Moreover, this is the order of thinking adopted by men
in their inward meditations. (2) The reasons for its rare employment
in investigations of nature are to be found in current misconceptions,
whereof we shall examine the causes hereafter in our philosophy.
(3) Moreover, it demands, as we shall show, a keen and accurate
discernment. (4) Lastly, it is hindered by the conditions of human
life, which are, as we have already pointed out, extremely changeable.
(5) There are also other obstacles, which we will not here inquire into.


[46] (1) If anyone asks why I have not at the starting-point set forth
all the truths of nature in their due order, inasmuch as truth is
self-evident, I reply by warning him not to reject as false any
paradoxes he may find here, but to take the trouble to reflect on
the chain of reasoning by which they are supported; he will then
be no longer in doubt that we have attained to the truth.
(2) This is why I have as above.

[47] (1) If there yet remains some sceptic, who doubts of our
primary truth, and of all deductions we make, taking such truth
as our standard, he must either be arguing in bad faith, or we
must confess that there are men in complete mental blindness