たしかに町の家屋全部を，ちがったやり方で作り直し，通りをもっと美しくするという目的だけで，すべて取り壊してしまうことは見かけられない。しかし多くの人が，建て直しのために自分の家を取りつぶさせる。そればかりか，倒壊の恐れがあったり土台が十分にしっかりしていないときに取り壊さざるをえないのは，よく見られる。こうした実例から，わたしは次のように確信した。一個人が国家を，その根底からすべて変えたり，正しく建て直すために転覆したりして改造しようとすることは，まったく理に反しているし，さらに同様に，学問の全体系や，その教育のために学校で確立している秩序を改変しようとするのも理に反している，と。けれども，わたしがその時までに受け入れ信じてきた諸見解すべてにたいしては，自分の信念から一度きっぱりと取り除いてみることが最善だ，と。後になって，ほかのもっとよい見解を改めて取り入れ，前と同じものでも理性の基準に照らして正しくしてから取り入れるためである。古い基礎の上だけに建設し，若いころに信じ込まされた諸原理にだけ，それが真かどうか吟味もせずに依拠するより，このやり方によって，はるかによく自分の生を導いていくことに成功すると堅く信じた。なぜなら，この場合にもさまざまの困難があるにせょ，対応策もあり，公のど〈小さなことを改革する際にも見られる困難とは比べものにならなかったからだ。そうした公の大きな組織は，いったん倒されると再建は至難で，たんに動揺を受けた場合も，もちこたえることさえ困難をきわめ，しかもその崩壊はきわめて苛酷なものにならざるをえない。さらに，こうした大きな組織の不完全な点についていえば，これらが種々異なっていることだけでも，欠点が多いことを十分確かめられるが，こんな欠点があっても，習慣がそれらの欠点を大きく緩和してきたのは間違いない。しかも習慣は知らず知らずのうちに，欠点の多くを避けたり正したりしてきた。思慮分別だけではこれらの欠点にたいして，これほどうまく対処することはできないだろう。最後に，これらの欠点はたいてい，その組織を変革するより我慢しやすい。山々のあいだをうねっていた街道が，往来が激しければ，少しずつ平らに踏みならされて通りやすくなり，近道をしようと岩の上によじ登ったり崖の底へ降りたりするよりも，この広い街道を行くほうがはるかによいのと同じである。
It is true, however, that it is not customary
to pull down all the houses of a town with
the single design of rebuilding them differently,
and thereby rendering the streets more handsome;
but it often happens that a private individual
takes down his own with the view of erecting
it anew, and that people are even sometimes
constrained to this when their houses are
in danger of falling from age, or when the
foundations are insecure. With its before
me by way of example, I was persuaded that
it would indeed be preposterous for a private
individual to think of reforming a state
by fundamentally changing it throughout,
and overturning it in order to set it up
amended; and the same I thought was true
of any similar project for reforming the
body of the Sciences, or the order of teaching
them established in the Schools: but as for
the opinions which up to that time I had
embraced, I thought that I could not do better
than resolve at once to sweep them wholly
away, that I might afterwards be in a position
to admit either others more correct, or even
perhaps the same when they had undergone
the scrutiny of Reason. I firmly believed
that in this way I should much better succeed
in the conduct of my life, than if I built
only upon old foundations, and leant upon
principles which, in my youth, I had taken
upon trust. For although I recognised various
difficulties in this undertaking, these were
not, however, without remedy, nor once to
be compared with such as attend the slightest
reformation in public affairs. Large bodies,
if once overthrown are with great difficulty
set up again, or even kept erect when once
seriously shaken, and the fall of such is
always disastrous. Then if there are any
imperfections in the constitutions of states,
(and that many such exists the diversity
of constitutions is alone sufficient to assure
us,) custom has without doubt materially
smoothed their inconveniences, and has even
managed to steer altogether clear of, or
sensibly corrected a number which sagacity
could not have provided against with equal
effect; and, in fine, the defects are almost
always more tolerable than the change necessary
for their removal; in the same manner that
highways which wind among mountains, by being
much frequented, become gradually so smooth
and commodious, that it is much better to
follow them than to seek a straighter path
by climbing over the tops of rocks and descending
to the bottoms of precipices.