これらすべてのことを，わたしは先に出版するつもりだった論文で，個々に十分くわしく説明した。それにつづいて次のことも示した。たとえば，首が切り落とされた直後，もはや生命はなくなっているのになお動いて，地面に喰いついたりするのが見られるように，動物精気が人体の内部にあって肢体を動かす力を持つょぅになるためには，人体の神経と筋肉の構造はどのようでなければならないか。覚醒，睡眠，夢を引き起こすには，脳内でどういう変化が起こっているはずか。光，音，匂い，味，熱その他の外的対象のあらゆる性質は，どのようにして，感覚を介して脳にさまざまな観念を刻みつけることができるのか。飢え，渇きその他の内的情念も，どのようにしてその観念を脳に送ることができるのか。脳内でこれらの観念が受容される共通感覚とみなされるべきものは何か。そうした観念を保存する記憶とはどういうものか。さらに観念をさまざまに変えて，新しい観念を組み立てたりできる想像力とは何か。この想像力は，また同じように，動物精気を筋肉に配分することにょつて，この肢体を，さまざまなふうに，かつ感覚に現れる対象と身体のなかにある内的情念に応じて，動かすことができ，それはわれわれの肢体が意志に導かれることなしに動くのと同じ程度にできる。以上のことは，人間の巧知がいかに多種多様のオートマットつまり自動機械を作りうるかを知る人たちには，少しも奇異には映らないだろう。この人たちは，各動物の体内には骨，筋肉，神経，動脈，静脈，その他あらゆる部分が無数にあり，それに比べれば実にわずかの部品しか使わずに，人間の巧知がどれほど多種多様のオートマットを作りうるかを知って，この人体を，神の手によって作られ，人間が発明できるどんな機械よりも，比類なく整えられ，みごとな運動を自らなしうる一つの機械とみなすであろう。
I had expounded all these matters which sufficient
minuteness in the Treatise which I formerly
thought of publishing. And after these, I
had shewn what must be the fabric of the
nerves and muscles of the human body to give
the animal spirits contained in it the power
to move the members, as when we see heads
shortly after they have been struck off still
move and bite the earth, although no longer
animated; what changes must take place in
the brain to produce waking, sleep, and dreams;
how light, sounds, odours, tastes, heat,
and all the other qualities of external objects
impress it with different ideas by means
of the senses; how hunger, thirst, and the
other internal affections can likewise impress
upon it divers ideas; what must be understood
by the common sense (sensus communis) in
which these ideas are received, by the memory
which retains them, by the fantasy which
can change them in various ways, and out
of them compose new ideas, and which, by
the same means, distributing the animal spirits
through the muscles, can cause the members
of such a body to move in as many different
ways, and in a manner as suited, whether
to the objects that are presented to its
senses or to its internal affections, as
can take place in our own case apart from
the guidance of the will. Nor will this appear
at all strange to those who are acquainted
with the variety of movements performed by
the different automata, or moving machines
fabricated by human industry, and that with
help of but few pieces compared with the
great multitude of bones, muscles, nerves,
arteries, veins, and other parts that are
found in the body of each animal. Such persons
will look upon this body as a machine made
by the hands of God, which is incomparably
better arranged, and adequate to movements
more admirable than is any machine of human
invention. And here I specially stayed to
show that, were there such machines exactly
resembling in organs and outward form an
ape or any other irrational animal, we could
have no means of knowing that they were in
any respect of a different nature from these
animals; but if there were machines bearing
the image of our bodies, and capable of imitating
our actions as far as it is morally possible,
there would still remain two most certain
tests whereby to know that they were not
therefore really men. Of these the first
is that they could never use words or other
signs arranged in such a manner as is competent
to us in order to declare our thoughts to
others; for we may easily conceive a machine
to be so constructed that it emits vocables,
and even that it emits some correspondent
to the action upon it of external objects
which cause a change in its organs; for example,
if touched in a particular place it may demand
what we wish to say to it; if in another
it may cry out that it is hurt, and such
like; but not that it should arrange them
variously so as appositely to reply to what
is said in its presence, as men of the lowest
grade of intellect can do. The second test
is, that although such machines might execute
many things with equal or perhaps greater
perfection than any of us, they would, without
doubt, fail in certain others from which
it could be discovered that they did not
act from knowledge, but solely from the disposition
of their organs: for while Reason is an universal
instrument that is alike available on every
occasion, these organs, on the contrary,
need a particular arrangement for each particular
action; whence it must be morally impossible
that there should exist in any machine a
diversity of organs sufficient to enable
it to act in all the occurrences of life,
in the way in which our reason enables us
to act. Again, by means of these two tests
we may likewise know the difference between
men and brutes. For it is highly deserving
of remark, that there are no men so dull
and stupid, not even idiots, as to be incapable
of joining together different words, and
thereby constructing a declaration by which
to make their thoughts understood; and that
on the other hand, there is no other animal,
however perfect or happily circumstanced
which can do the like. Nor does this inability
arise from want of organs: for we observe
that magpies and parrots can utter words
like ourselves, and are yet unable to speak
as we do, that is, so as to show that they
understand what they say; in place of which
men born deaf and dumb, and thus not less,
but rather more than the brutes, destitute
of the organs which others use in speaking,
are in the habit of spontaneously inventing
certain signs by which they discover their
thoughts to those who, being usually in their
company, have leisure to learn their language.
And this proves not only that the brutes
have less Reason than man, but that they
have none at all: for we see that very little
is required to enable a person to speak;
and since a certain inequality of capacity
is observable among animals of the same species,
as well as among men, and since some are
more capable of being instructed than others,
it is incredible that the most perfect ape
or parrot of its species, should not in this
be equal to the most stupid infant of its
kind, or at least to one that was crack-brained,
unless the soul of brutes were of a nature
wholly different from ours. And we ought
not to confound speech with the natural movements
which indicate the passions, and can be imitated
by machines as well as manifested by animals;
nor must it be thought with certain of the
ancients, that the brutes speak, although
we do not understand their language. For
if such were the case, since they are endowed
with many organs analogous to ours, they
could as easily communicate their thoughts
to us as to their fellows. It is also very
worthy of remark, that, though there are
many animals which manifest more industry
than we in certain of their actions, the
same animals are yet observed to show none
at all in many others: so that the circumstance
that they do better than we does not prove
that they are endowed with mind, for it would
thence follow that they possessed greater
Reason than any of us, and could surpass
us in all things; on the contrary, it rather
proves that they are destitute of Reason,
and that it is Nature which acts in them
according to the disposition of their organs:
thus it is seen, that a clock composed only
of wheels and weights can number the hours
and measure time more exactly than we with
all our skill.