まだ若かった頃，哲学の諸部門のうちでは論理学を・数学のうちでは幾何学者の解析と代数を，少し熱心に学んだ。この三つの技術ないし学問は，わたしの計画にきっと何か力を与えてくれると思われたのだ。しかし，それらを検討して次のことに気がついた。まず論理学は，その三段論法も他の大部分の教則も，未知のことを学ぶのに役立つのではなく，むしろ，既知のことを他人に説明したり，そればかりか，ルルスの術のように，知らないことを何の判断も加えず語るのに役立つだけだ。実際，論理学は，いかにも真実で有益なたくさんの規則を含んではいるが，なかには有害だったり余計だったりするものが多くまじっていて，それらを選り分けるのは，まだ下削りもしていない大理石の塊からダイアナやミネルヴァの像を彫り出すのと同じくらい難しい。次に古代人の解析と現代人の代数は，両者とも，ひどく抽象的で何の役にも立たないことにだけ用いられている。そのうえ解析はつねに図形の考察に縛りつけられているので，知性を働かせると，想像力をひどく疲れさせてしまう。そして代数では，ある種の規則とある種の記号にやたらにとらわれてきたので，精神を培う学問どころか，かえって精神を混乱におとしいれる，錯雑で不明瞭な術になってしまった。以上の理由でわたしは，この三つの学問の長所を含みながら，その欠点を免れている何か他の方法を探求しなければ，と考えた。法律の数がやたらに多いと，しばしば悪徳に口実をあたえるので，国家は，ごくわずかの法律が遵守されるときのほうがずっとよく統治される。同じように，論理学を構成しているおびただしい規則の代わりに，一度たりともそれから外れまいという堅い不変の決心をするなら，次の四つの規則で十分だと信じた。
Among the branches of Philosophy, I had,
at an earlier period, given some attention
to Logic, and among those of the Mathematics
to Geometrical Analysis and Algebra,?three
Arts or Sciences which ought, as I conceived,
to contribute something to my design. But,
on examination, I found that, as for Logic,
its syllogisms and the majority of its other
precepts are of avail rather in the communication
of what we already know, or even as the Art
of Lully, in speaking without judgment of
things of which we are ignorant, than in
the investigation of the unknown; and although
this Science contains indeed a number of
correct and very excellent precepts, there
are, nevertheless, so many others, and these
either injurious or superfluous, mingled
with the former, that it is almost quite
as difficult to effect a severance of the
true from the false as it is to extract a
Diana or a Minerva from a rough block of
marble. Then as to the Analysis of the ancients
and the Algebra of the moderns, besides that
they embrace only matters highly abstract,
and, to appearance, of no use, the former
is so exclusively restricted to the consideration
of figures, that it can exercise the Understanding
only on condition of greatly fatiguing the
Imagination; 2 and, in the latter, there
is so complete a subjection to certain rules
and formulas, that there results an art full
of confusion and obscurity calculated to
embarrass, instead of a science fitted to
cultivate the mind. By these considerations
I was induced to seek some other Method which
would comprise the advantages of the three
and be exempt from their defects. And as
a multitude of laws often only hampers justice,
so that a state is best governed when, with
few laws, these are rigidly administered;
in like manner, instead of the great number
of precepts of which Logic is composed, I
believed that the four following would prove
perfectly sufficient for me, provided I took
the firm and unwavering resolution never
in a single instance to fail in observing
them.