第一は，わたしが明証的に真であると認めるのでなければ，どんなことも真として受け入れないことだった。言い換えれば，注意ぶかく速断と偏見を避けること，そして疑いをさしはさむ余地のまったくないほど明断かつ判明に精神に現れるもの以外は，何もわたしの判断のなかに含めないこと。
第二は，わたしが検討する難問の一つ一つを，できるだけ多くの，しかも問題をよりょく解くために必要なだけの小部分に分割すること。
第三は，わたしの思考を順序にしたがって導くこと。そこでは，もっとも単純でもっとも認識しやすいものから始めて，少しずつ，階段を昇るようにして，もっとも複雑なものの認識にまで昇っていき，自然のままでは互いに前後の順序がつかないものの間にさえも順序を想定して進むこと。
そして最後は，すべての場合に，完全な枚挙と全体にわたる見直しをして，なにも見落とさなかったと確信すること。
The first was never to accept anything for
true which I did not clearly know to be such;
that is to say, carefully to avoid precipitancy
and prejudice, and to comprise nothing more
in my judgment than what was presented to
my mind so clearly and distinctly as to exclude
all ground of doubt.
The second, to divide each of the difficulties
under examination into as many parts as possible,
and as might be necessary for its adequate
solution.
The third, to conduct my thoughts in such
order that, by commencing with objects the
simplest and easiest to know, I might ascend
by little and little, and, as it were, step
by step, to the knowledge of the more complex;
assigning in thought a certain order even
to those objects which in their own nature
do not stand in a relation of antecedence
and sequence.
And the last, in every case to make enumerations
so complete, and reviews so general, that
I might be assured that nothing was omitted.