the origination of living beings-第3章

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open；　but　by　a　train　of　reasoning　involving　many　Inductions　and
Deductions；　you　have　probably　arrived　long　before　at　the　General
Lawand　a　very　good　one　it　isthat　windows　do　not　open　of　themselves；
and　you　therefore　conclude　that　something　has　opened　the　window。　　A
second　general　law　that　you　have　arrived　at　in　the　same　way　is；　that
tea…pots　and　spoons　do　not　go　out　of　a　window　spontaneously；　and　you
are　satisfied　that；　as　they　are　not　now　where　you　left　them；　they　have
been　removed。　　In　the　third　place；　you　look　at　the　marks　on　the
window…sill；　and　the　shoemarks　outside；　and　you　say　that　in　all
previous　experience　the　former　kind　of　mark　has　never　been　produced　by
anything　else　but　the　hand　of　a　human　being；　and　the　same　experience
shows　that　no　other　animal　but　man　at　present　wears　shoes　with
hob…nails　on　them　such　as　would　produce　the　marks　in　the　gravel。　　I　do
not　know；　even　if　we　could　discover　any　of　those　〃missing　links〃　that
are　talked　about；　that　they　would　help　us　to　any　other　conclusion！　　At
any　rate　the　law　which　states　our　present　experience　is　strong　enough
for　my　present　purpose。You　next　reach　the　conclusion；　that　as　these
kinds　of　marks　have　not　been　left　by　any　other　animals　than　men；　or　are
liable　to　be　formed　in　any　other　way　than　by　a　man's　hand　and　shoe；　the
marks　in　question　have　been　formed　by　a　man　in　that　way。　　You　have；
further；　a　general　law；　founded　on　observation　and　experience；　and
that；　too；　is；　I　am　sorry　to　say；　a　very　universal　and　unimpeachable
one；that　some　men　are　thieves；　and　you　assume　at　once　from　all　these
premissesand　that　is　what　constitutes　your　hypothesisthat　the　man
who　made　the　marks　outside　and　on　the　window…sill；　opened　the　window；
got　into　the　room；　and　stole　your　tea…pot　and　spoons。　　You　have　now
arrived　at　a　'Vera　Causa'；you　have　assumed　a　Cause　which　it　is　plain
is　competent　to　produce　all　the　phenomena　you　have　observed。　　You　can
explain　all　these　phenomena　only　by　the　hypothesis　of　a　thief。　　But
that　is　a　hypothetical　conclusion；　of　the　justice　of　which　you　have　no
absolute　proof　at　all；　it　is　only　rendered　highly　probable　by　a　series
of　inductive　and　deductive　reasonings。

I　suppose　your　first　action；　assuming　that　you　are　a　man　of　ordinary
common　sense；　and　that　you　have　established　this　hypothesis　to　your　own
satisfaction；　will　very　likely　be　to　go　off　for　the　police；　and　set
them　on　the　track　of　the　burglar；　with　the　view　to　the　recovery　of　your
property。　　But　just　as　you　are　starting　with　this　object；　some　person
comes　in；　and　on　learning　what　you　are　about；　says；　〃My　good　friend；
you　are　going　on　a　great　deal　too　fast。　　How　do　you　know　that　the　man
who　really　made　the　marks　took　the　spoons？　　It　might　have　been　a　monkey
that　took　them；　and　the　man　may　have　merely　looked　in　afterwards。〃　　You
would　probably　reply；　〃Well；　that　is　all　very　well；　but　you　see　it　is
contrary　to　all　experience　of　the　way　tea…pots　and　spoons　are
abstracted；　so　that；　at　any　rate；　your　hypothesis　is　less　probable　than
mine。〃　　While　you　are　talking　the　thing　over　in　this　way；　another　friend
arrives；　one　of　that　good　kind　of　people　that　I　was　talking　of　a　little
while　ago。　　And　he　might　say；　〃Oh；　my　dear　sir；　you　are　certainly　going
on　a　great　deal　too　fast。　　You　are　most　presumptuous。　　You　admit　that
all　these　occurrences　took　place　when　you　were　fast　asleep；　at　a　time
when　you　could　not　possibly　have　known　anything　about　what　was　taking
place。　　How　do　you　know　that　the　laws　of　Nature　are　not　suspended
during　the　night？　　It　may　be　that　there　has　been　some　kind　of
supernatural　interference　in　this　case。〃　　In　point　of　fact；　he　declares
that　your　hypothesis　is　one　of　which　you　cannot　at　all　demonstrate　the
truth；　and　that　you　are　by　no　means　sure　that　the　laws　of　Nature　are
the　same　when　you　are　asleep　as　when　you　are　awake。

Well；　now；　you　cannot　at　the　moment　answer　that　kind　of　reasoning。　　You
feel　that　your　worthy　friend　has　you　somewhat　at　a　disadvantage。　　You
will　feel　perfectly　convinced　in　your　own　mind；　however；　that　you　are
quite　right；　and　you　say　to　him；　〃My　good　friend；　I　can　only　be　guided
by　the　natural　probabilities　of　the　case；　and　if　you　will　be　kind　enough
to　stand　aside　and　permit　me　to　pass；　I　will　go　and　fetch　the　police。〃
Well；　we　will　suppose　that　your　journey　is　successful；　and　that　by　good
luck　you　meet　with　a　policeman；　that　eventually　the　burglar　is　found
with　your　property　on　his　person；　and　the　marks　correspond　to　his　hand
and　to　his　boots。　　Probably　any　jury　would　consider　those　facts　a　very
good　experimental　verification　of　your　hypothesis；　touching　the　cause
of　the　abnormal　phenomena　observed　in　your　parlour；　and　would　act
accordingly。

Now；　in　this　suppositious　case；　I　have　taken　phenomena　of　a　very　common
kind；　in　order　that　you　might　see　what　are　the　different　steps　in　an
ordinary　process　of　reasoning；　if　you　will　only　take　the　trouble　to
analyse　it　carefully。　　All　the　operations　I　have　described；　you　will
see；　are　involved　in　the　mind　of　any　man　of　sense　in　leading　him　to　a
conclusion　as　to　the　course　he　should　take　in　order　to　make　good　a
robbery　and　punish　the　offender。　　I　say　that　you　are　led；　in　that　case；
to　your　conclusion　by　exactly　the　same　train　of　reasoning　as　that　which
a　man　of　science　pursues　when　he　is　endeavouring　to　discover　the　origin
and　laws　of　the　most　occult　phenomena。　　The　process　is；　and　always　must
be；　the　same；　and　precisely　the　same　mode　of　reasoning　was　employed　by
Newton　and　Laplace　in　their　endeavours　to　discover　and　define　the
causes　of　the　movements　of　the　heavenly　bodies；　as　you；　with　your　own
common　sense；　would　employ　to　detect　a　burglar。　　The　only　difference
is；　that　the　nature　of　the　inquiry　being　more　abstruse；　every　step　has
to　be　most　carefully　watched；　so　that　there　may　not　be　a　single　crack
or　flaw　in　your　hypothesis。　　A　flaw　or　crack　in　many　of　the　hypotheses
of　daily　life　may　be　of　little　or　no　moment　as　affecting　the　general
correctness　of　the　conclusions　at　which　we　may　arrive；　but；　in　a
scientific　inquiry；　a　fallacy；　great　or　small；　is　always　of　importance；
and　is　sure　to　be　constantly　productive　of　mischievous；　if　not　fatal
results。

Do　not　allow　yourselves　to　be　misled　by　the　common　notion　that　an
hypothesis　is　untrustworthy　simply　because　it　is　an　hypothesis。　　It　is
often　urged；　in　respect　to　some　scientific　conclusion；　that；　after　all；
it　is　only　an　hypothesis。　　But　what　more　have　we　to　guide　us　in
nine…tenths　of　the　most　important　affairs　of　daily　life　than　hypotheses；
and　often　very　ill…based　ones？　　So　that　in　science；　where　the　evidence
of　an　hypothesis　is　subjected　to　the　most　rigid　examination；　we　may
rightly　pursue　the　same　course。　　You　may　have　hypotheses　and
hypotheses。　　A　man　may　say；　if　he　likes；　that　the　moon　is　made　of　green
cheese：　that　is　an　hypothesis。　　But　another　man；　who　has　devoted　a
great　deal　of　time　and　attention　to　the　subject；　and　availed　himself　of
the　most　powerful　telescopes　and　the　results　of　the　observations　of
others；　declares　that　in　his　opinion　it　is　probably　composed　of
materials　very　similar　to　those　of　which　our　own　earth　is　made　up：　and
that　is　also　only　an　hypothesis。　　But　I　need　not　tell　you　that　there　is
an　enormous　difference　in　the　value　of　the　two　hypotheses。　　That　one
which　is　based　on　sound　scientific　knowledge　is　sure　to　have　a
corresponding　value；　and　that　which　is　a　mere　hasty　random　guess　is
likely　to　have　but　little　value。　　Every　great　step　in　our　progress　in
discovering　causes　has　been　made　in　exactly　the　same　way　as　that　which　I
have　detailed　to　you。　　A　person　observing　the　occurrence　of　certain
facts　and　phenomena　asks；　naturally　enough；　what　process；　what　kind　of
operation　known　to　occur　in　nature　applied　to　the　particular　case；　will
unravel　and　explain　the　mystery？　　Hence　you　have　the　scientific
hypothesis；　and　its　value　will　be　proportionate　to　the　care　and
completeness　with　which　its　basis　had　been　tested　and　verified。　　It　is
in　these　matters　as　in　the　commonest　affairs　of　practical　life：　the
guess　of　the　fool　will　be　folly；　while　the　guess　of　the　wise　man　will
contain　wisdom。　　In　all　cases；　you　see　that　the　value　of　the　result
depends　on　the　pat