わたしは自分の精神から出たものを重く見たことは一度もない。自分が用いる方法で成果を収めたことが，理論的学問に属するある難問について満足を得たとか，この方法の教える論拠によって自分の生き方を律しようと努めたとかだけで，ほかに何の成果も収めていなかった間は，この方法について何か書かねばならないとは思わなかった。というのは，生き方については，だれもが十分に自分の見識をもっているために，人間の頭数と同じだけの改革者が現れることになりかねないからだ――この方面で何かの変革を企てることが，神がその民の主権者に任じたり，預言者たるに十分な恩寵と篤い信仰心を与えた人だけでなく，ほかの人たちにも許されるとしたらではあるが。また，わたしの思索が大いに自分の気に入ったとはいえ，他人もまたおそらく，それ以上に気に入った自分なりの思索をもっていると思ったからだ。しかし，自然学にかんしていくつかの蔑的知見を獲得し・それらをさまざまな特殊問題に試しはじめながら，これらの知見がわれわれをどこまで導きうるか，また今まで一般に用いられてきた諸原理とどんなに異なっているかに気がついてすぐ，わたしは，これらを隠しておくことは，力の及ぶかぎり万人の一般的幸福をはかるべし，という淀に照らして大きな罪を犯すことになる，と思った。なぜなら，これらの知見は次のことをわたしに理解させたから。すなわち，われわれが人生にきわめて有用な知識に到達することが可能であり，学校で教えているあの思弁哲学の代わりに，実践的な哲学を見いだすことができ，この実践的な哲学によって，火，水，空気，星，天空その他われわれをとりまくすべての物体の力や作用を，職人のさまざまな技能を知るょぅにはっきりと知って，同じようにしてそれらの物体をそれぞれ適切な用途にもちいることができ，こうしてわれわれをいわば自然の主人にして所有者たらしめることである。このことは，たんに大地の実りと地上のあらゆる便宜を，やすやすと享受させる無数の技術を発明するために望ましいだけではない。主として，健康を維持するためにも望ましいのである。健康はまぎれもなくこの世で最上の善であり，ほかのあらゆる善の基礎である。というのは，精神でさえも体質と身体器官の状態とに多分に依存しているため，人間たちを共通に今までよりもいっそう賢明で有能にする何らかの手段を見いだすことが可能だとすれば，その手段は医学のなかにこそ求めるべきだとわたしは信じているからだ。なるほど，現在おこなわれている医学にそれほど効用の著しいものはほとんど含まれていない。しかし，わたしは医学を軽蔑するつもりは少しもないのだが，次のことを確信している。これまでの医学で知られているすべてのことは，今後に知るべく残されているものに比べたら，ほとんど無に等しいと，だれもが，医学を職業としている人たちさえも認めている。身体ならびに精神の無数の病気，そしておそらくは老衰さえも，われわれがその原因を知り，自然が提供してくれる医薬すべてについて十分な知識を持つならば，免れうろことである。ところでわたしは，これほどに重要不可欠な学問の探究に全生涯を当てようと企て，わたしの見いだした道が，人生の短さと実験の不足とによって妨げられさえしなければ，その道をたどって間違いなくその学問が発見されるはずだと思われたので，この二つの障害に対して次のこと以上によい策はないと判断した。それは，自分の発見したことがどんなにささやかでも，すべてを忠実に公衆に伝え，すぐれた精神の持ち主がさらに先に進むように促すことだ。その際，各自がその性向と能力に従い，必要な実験に協力し，知り得たすべてを公衆に伝えるのである。先の者が到達した地点から後の者が始め，こうして多くの人の生涯と業績を合わせて，われわれ全体で，各人が別々になしうるよりもはるかに遠くまで進むことができるようにするのである。
I have never made much account of what has
proceeded from my own mind; and so long as
I gathered no other advantage from the Method
I employ beyond satisfying myself on some
difficulties belonging to the speculative
sciences, or endeavouring to regulate my
actions according to the principles it taught
me, I never thought myself bound to publish
anything respecting it. For in what regards
manners, every one is so full of his own
wisdom, that there might be found as many
reformers as heads, if any were allowed to
take upon themselves the task of mending
them, except those whom God has constituted
the supreme rulers of his people, or to whom
he has given sufficient grace and zeal to
be prophets; and although my speculations
greatly pleased myself, I believed that others
had theirs, which perhaps pleased them still
more. But as soon as I had acquired some
general notions respecting Physics, and beginning
to make trial of them in various particular
difficulties, had observed how far they can
carry us, and how much they differ from the
principles that have been employed up to
the present time, I believed that I could
not keep them concealed without sinning grievously
against the law by which we are bound to
promote, as far as in us lies, the general
good of mankind. For by them I perceived
it to be possible to arrive at knowledge
highly useful in life; and in room of the
Speculative Philosophy usually taught in
the Schools, to discover a Practical, by
means of which, knowing the force and action
of fire, water, air, the stars, the heavens,
and all the other bodies that surround us,
as distinctly as we know the various crafts
of our artizans, we might also apply them
in the same way to all the uses to which
they are adapted, and thus render ourselves
the lords and possessors of nature. And this
is a result to be desired, not only in order
to the invention of an infinity of arts,
by which we might be enabled to enjoy without
any trouble the fruits of the earth, and
all its comforts, but also and especially
for the preservation of health, which is
without doubt, of all the blessings of this
life, the first and fundamental one; for
the mind is so intimately dependent upon
the condition and relation of the organs
of the body, that if any means can ever be
found to render men wiser and more ingenious
than hitherto, I believe that it is in Medicine
they must be sought for. It is true that
the science of Medicine, as it now exists,
contains few things whose utility is very
remarkable: but without any wish to depreciate
it, I am confident that there is no one,
even among those whose profession it is,
who does not admit that all at present known
in it is almost nothing in comparison of
what remains to be discovered; and that we
could free ourselves from an infinity of
maladies of body as well as of mind, and
perhaps also even from the debility of age,
if we had sufficiently ample knowledge of
their causes, and of all the remedies provided
for us by Nature. But since I designed to
employ my whole life in the search after
so necessary a Science, and since I had fallen
in with a path which seems to me such, that
if any one follow it he must inevitably reach
the end desired, unless he be hindered either
by the shortness of life or the want of experiments,
I judged that there could be no more effectual
provision against these two impediments than
if I were faithfully to communicate to the
public all the little I might myself have
found, and incite men of superior genius
to strive to proceed farther, by contributing,
each according to his inclination and ability,
to the experiments which it would be necessary
to make, and also by informing the public
of all they might discover, so that, by the
last beginning where those before them had
left off, and thus connecting the lives and
labours of many, we might collectively proceed
much farther than each by himself could do.