Lectures¡¡on¡¡Evolution
by¡¡Thomas¡¡Henry¡¡Huxley
I
THE¡¡THREE¡¡HYPOTHESES¡¡RESPECTING¡¡THE¡¡HISTORY¡¡OF¡¡NATURE
We¡¡live¡¡in¡¡and¡¡form¡¡part¡¡of¡¡a¡¡system¡¡of¡¡things¡¡of¡¡immense
diversity¡¡and¡¡perplexity£»¡¡which¡¡we¡¡call¡¡Nature£»¡¡and¡¡it¡¡is¡¡a
matter¡¡of¡¡the¡¡deepest¡¡interest¡¡to¡¡all¡¡of¡¡us¡¡that¡¡we¡¡should¡¡form
just¡¡conceptions¡¡of¡¡the¡¡constitution¡¡of¡¡that¡¡system¡¡and¡¡of¡¡its
past¡¡history¡£¡¡With¡¡relation¡¡to¡¡this¡¡universe£»¡¡man¡¡is£»¡¡in¡¡extent£»
little¡¡more¡¡than¡¡a¡¡mathematical¡¡point£»¡¡in¡¡duration¡¡but¡¡a
fleeting¡¡shadow£»¡¡he¡¡is¡¡a¡¡mere¡¡reed¡¡shaken¡¡in¡¡the¡¡winds¡¡of¡¡force¡£
But¡¡as¡¡Pascal¡¡long¡¡ago¡¡remarked£»¡¡although¡¡a¡¡mere¡¡reed£»¡¡he¡¡is¡¡a
thinking¡¡reed£»¡¡and¡¡in¡¡virtue¡¡of¡¡that¡¡wonderful¡¡capacity¡¡of
thought£»¡¡he¡¡has¡¡the¡¡power¡¡of¡¡framing¡¡for¡¡himself¡¡a¡¡symbolic
conception¡¡of¡¡the¡¡universe£»¡¡which£»¡¡although¡¡doubtless¡¡highly
imperfect¡¡and¡¡inadequate¡¡as¡¡a¡¡picture¡¡of¡¡the¡¡great¡¡whole£»¡¡is¡¡yet
sufficient¡¡to¡¡serve¡¡him¡¡as¡¡a¡¡chart¡¡for¡¡the¡¡guidance¡¡of¡¡his
practical¡¡affairs¡£¡¡It¡¡has¡¡taken¡¡long¡¡ages¡¡of¡¡toilsome¡¡and¡¡often
fruitless¡¡labour¡¡to¡¡enable¡¡man¡¡to¡¡look¡¡steadily¡¡at¡¡the¡¡shifting
scenes¡¡of¡¡the¡¡phantasmagoria¡¡of¡¡Nature£»¡¡to¡¡notice¡¡what¡¡is¡¡fixed
among¡¡her¡¡fluctuations£»¡¡and¡¡what¡¡is¡¡regular¡¡among¡¡her¡¡apparent
irregularities£»¡¡and¡¡it¡¡is¡¡only¡¡comparatively¡¡lately£»¡¡within¡¡the
last¡¡few¡¡centuries£»¡¡that¡¡the¡¡conception¡¡of¡¡a¡¡universal¡¡order¡¡and
of¡¡a¡¡definite¡¡course¡¡of¡¡things£»¡¡which¡¡we¡¡term¡¡the¡¡course¡¡of
Nature£»¡¡has¡¡emerged¡£
But£»¡¡once¡¡originated£»¡¡the¡¡conception¡¡of¡¡the¡¡constancy¡¡of¡¡the
order¡¡of¡¡Nature¡¡has¡¡become¡¡the¡¡dominant¡¡idea¡¡of¡¡modern¡¡thought¡£
To¡¡any¡¡person¡¡who¡¡is¡¡familiar¡¡with¡¡the¡¡facts¡¡upon¡¡which¡¡that
conception¡¡is¡¡based£»¡¡and¡¡is¡¡competent¡¡to¡¡estimate¡¡their
significance£»¡¡it¡¡has¡¡ceased¡¡to¡¡be¡¡conceivable¡¡that¡¡chance¡¡should
have¡¡any¡¡place¡¡in¡¡the¡¡universe£»¡¡or¡¡that¡¡events¡¡should¡¡depend
upon¡¡any¡¡but¡¡the¡¡natural¡¡sequence¡¡of¡¡cause¡¡and¡¡effect¡£¡¡We¡¡have
come¡¡to¡¡look¡¡upon¡¡the¡¡present¡¡as¡¡the¡¡child¡¡of¡¡the¡¡past¡¡and¡¡as
the¡¡parent¡¡of¡¡the¡¡future£»¡¡and£»¡¡as¡¡we¡¡have¡¡excluded¡¡chance¡¡from¡¡a
place¡¡in¡¡the¡¡universe£»¡¡so¡¡we¡¡ignore£»¡¡even¡¡as¡¡a¡¡possibility£»¡¡the
notion¡¡of¡¡any¡¡interference¡¡with¡¡the¡¡order¡¡of¡¡Nature¡£
Whatever¡¡may¡¡be¡¡men's¡¡speculative¡¡doctrines£»¡¡it¡¡is¡¡quite¡¡certain
that¡¡every¡¡intelligent¡¡person¡¡guides¡¡his¡¡life¡¡and¡¡risks¡¡his
fortune¡¡upon¡¡the¡¡belief¡¡that¡¡the¡¡orderof¡¡Nature¡¡is¡¡constant£»¡¡and
that¡¡the¡¡chain¡¡of¡¡natural¡¡causation¡¡is¡¡never¡¡broken¡£
In¡¡fact£»¡¡no¡¡belief¡¡which¡¡we¡¡entertain¡¡has¡¡so¡¡complete¡¡a¡¡logical
basis¡¡as¡¡that¡¡to¡¡which¡¡I¡¡have¡¡just¡¡referred¡£¡¡It¡¡tacitly
underlies¡¡every¡¡process¡¡of¡¡reasoning£»¡¡it¡¡is¡¡the¡¡foundation¡¡of
every¡¡act¡¡of¡¡the¡¡will¡£¡¡It¡¡is¡¡based¡¡upon¡¡the¡¡broadest¡¡induction£»
and¡¡it¡¡is¡¡verified¡¡by¡¡the¡¡most¡¡constant£»¡¡regular£»¡¡and¡¡universal
of¡¡deductive¡¡processes¡£¡¡But¡¡we¡¡must¡¡recollect¡¡that¡¡any¡¡human
belief£»¡¡however¡¡broad¡¡its¡¡basis£»¡¡however¡¡defensible¡¡it¡¡may¡¡seem£»
is£»¡¡after¡¡all£»¡¡only¡¡a¡¡probable¡¡belief£»¡¡and¡¡that¡¡our¡¡widest¡¡and
safest¡¡generalisations¡¡are¡¡simply¡¡statements¡¡of¡¡the¡¡highest
degree¡¡of¡¡probability¡£¡¡Though¡¡we¡¡are¡¡quite¡¡clear¡¡about¡¡the
constancy¡¡of¡¡the¡¡order¡¡of¡¡Nature£»¡¡at¡¡the¡¡present¡¡time£»¡¡and¡¡in
the¡¡present¡¡state¡¡of¡¡things£»¡¡it¡¡by¡¡no¡¡means¡¡necessarily¡¡follows
that¡¡we¡¡are¡¡justified¡¡in¡¡expanding¡¡this¡¡generalisation¡¡into¡¡the
infinite¡¡past£»¡¡and¡¡in¡¡denying£»¡¡absolutely£»¡¡that¡¡there¡¡may¡¡have
been¡¡a¡¡time¡¡when¡¡Nature¡¡did¡¡not¡¡follow¡¡a¡¡fixed¡¡order£»¡¡when¡¡the
relations¡¡of¡¡cause¡¡and¡¡effect¡¡were¡¡not¡¡definite£»¡¡and¡¡when¡¡extra¡
natural¡¡agencies¡¡interfered¡¡with¡¡the¡¡general¡¡course¡¡of¡¡Nature¡£
Cautious¡¡men¡¡will¡¡allow¡¡that¡¡a¡¡universe¡¡so¡¡different¡¡from¡¡that
which¡¡we¡¡know¡¡may¡¡have¡¡existed£»¡¡just¡¡as¡¡a¡¡very¡¡candid¡¡thinker
may¡¡admit¡¡that¡¡a¡¡world¡¡in¡¡which¡¡two¡¡and¡¡two¡¡do¡¡not¡¡make¡¡four£»
and¡¡in¡¡which¡¡two¡¡straight¡¡lines¡¡do¡¡inclose¡¡a¡¡space£»¡¡may¡¡exist¡£
But¡¡the¡¡same¡¡caution¡¡which¡¡forces¡¡the¡¡admission¡¡of¡¡such
possibilities¡¡demands¡¡a¡¡great¡¡deal¡¡of¡¡evidence¡¡before¡¡it
recognises¡¡them¡¡to¡¡be¡¡anything¡¡more¡¡substantial¡£¡¡And¡¡when¡¡it¡¡is
asserted¡¡that£»¡¡so¡¡many¡¡thousand¡¡years¡¡ago£»¡¡events¡¡occurred¡¡in¡¡a
manner¡¡utterly¡¡foreign¡¡to¡¡and¡¡inconsistent¡¡with¡¡the¡¡existing
laws¡¡of¡¡Nature£»¡¡men£»¡¡who¡¡without¡¡being¡¡particularly¡¡cautious£»
are¡¡simply¡¡honest¡¡thinkers£»¡¡unwilling¡¡to¡¡deceive¡¡themselves¡¡or
delude¡¡others£»¡¡ask¡¡for¡¡trustworthy¡¡evidence¡¡of¡¡the¡¡fact¡£
Did¡¡things¡¡so¡¡happen¡¡or¡¡did¡¡they¡¡not£¿¡¡This¡¡is¡¡a¡¡historical
question£»¡¡and¡¡one¡¡the¡¡answer¡¡to¡¡which¡¡must¡¡be¡¡sought¡¡in¡¡the¡¡same
way¡¡as¡¡the¡¡solution¡¡of¡¡any¡¡other¡¡historical¡¡problem¡£
So¡¡far¡¡as¡¡I¡¡know£»¡¡there¡¡are¡¡only¡¡three¡¡hypotheses¡¡which¡¡ever
have¡¡been¡¡entertained£»¡¡or¡¡which¡¡well¡¡can¡¡be¡¡entertained£»
respecting¡¡the¡¡past¡¡history¡¡of¡¡Nature¡£¡¡I¡¡will£»¡¡in¡¡the¡¡first
place£»¡¡state¡¡the¡¡hypotheses£»¡¡and¡¡then¡¡I¡¡will¡¡consider¡¡what
evidence¡¡bearing¡¡upon¡¡them¡¡is¡¡in¡¡our¡¡possession£»¡¡and¡¡by¡¡what
light¡¡of¡¡criticism¡¡that¡¡evidence¡¡is¡¡to¡¡be¡¡interpreted¡£
Upon¡¡the¡¡first¡¡hypothesis£»¡¡the¡¡assumption¡¡is£»¡¡that¡¡phenomena¡¡of
Nature¡¡similar¡¡to¡¡those¡¡exhibited¡¡by¡¡the¡¡present¡¡world¡¡have
always¡¡existed£»¡¡in¡¡other¡¡words£»¡¡that¡¡the¡¡universe¡¡has¡¡existed£»
from¡¡all¡¡eternity£»¡¡in¡¡what¡¡may¡¡be¡¡broadly¡¡termed¡¡its
present¡¡condition¡£
The¡¡second¡¡hypothesis¡¡is¡¡that¡¡the¡¡present¡¡state¡¡of¡¡things¡¡has
had¡¡only¡¡a¡¡limited¡¡duration£»¡¡and¡¡that£»¡¡at¡¡some¡¡period¡¡in¡¡the
past£»¡¡a¡¡condition¡¡of¡¡the¡¡world£»¡¡essentially¡¡similar¡¡to¡¡that
which¡¡we¡¡now¡¡know£»¡¡came¡¡into¡¡existence£»¡¡without¡¡any¡¡precedent
condition¡¡from¡¡which¡¡it¡¡could¡¡have¡¡naturally¡¡proceeded¡£
The¡¡assumption¡¡that¡¡successive¡¡states¡¡of¡¡Nature¡¡have¡¡arisen£»
each¡¡without¡¡any¡¡relation¡¡of¡¡natural¡¡causation¡¡to¡¡an¡¡antecedent
state£»¡¡is¡¡a¡¡mere¡¡modification¡¡of¡¡this¡¡second¡¡hypothesis¡£
The¡¡third¡¡hypothesis¡¡also¡¡assumes¡¡that¡¡the¡¡present¡¡state¡¡of
things¡¡has¡¡had¡¡but¡¡a¡¡limited¡¡duration£»¡¡but¡¡it¡¡supposes¡¡that¡¡this
state¡¡has¡¡been¡¡evolved¡¡by¡¡a¡¡natural¡¡process¡¡from¡¡an¡¡antecedent
state£»¡¡and¡¡that¡¡from¡¡another£»¡¡and¡¡so¡¡on£»¡¡and£»¡¡on¡¡this
hypothesis£»¡¡the¡¡attempt¡¡to¡¡assign¡¡any¡¡limit¡¡to¡¡the¡¡series¡¡of
past¡¡changes¡¡is£»¡¡usually£»¡¡given¡¡up¡£
It¡¡is¡¡so¡¡needful¡¡to¡¡form¡¡clear¡¡and¡¡distinct¡¡notions¡¡of¡¡what¡¡is
really¡¡meant¡¡by¡¡each¡¡of¡¡these¡¡hypotheses¡¡that¡¡I¡¡will¡¡ask¡¡you¡¡to
imagine¡¡what£»¡¡according¡¡to¡¡each£»¡¡would¡¡have¡¡been¡¡visible¡¡to¡¡a
spectator¡¡of¡¡the¡¡events¡¡which¡¡constitute¡¡the¡¡history¡¡of¡¡the
earth¡£¡¡On¡¡the¡¡first¡¡hypothesis£»¡¡however¡¡far¡¡back¡¡in¡¡time¡¡that
spectator¡¡might¡¡be¡¡placed£»¡¡he¡¡would¡¡see¡¡a¡¡world¡¡essentially£»
though¡¡perhaps¡¡not¡¡in¡¡all¡¡its¡¡details£»¡¡similar¡¡to¡¡that¡¡which¡¡now
exists¡£¡¡The¡¡animals¡¡which¡¡existed¡¡would¡¡be¡¡the¡¡ancestors¡¡of
those¡¡which¡¡now¡¡live£»¡¡and¡¡similar¡¡to¡¡them£»¡¡the¡¡plants£»¡¡in¡¡like
manner£»¡¡would¡¡be¡¡such¡¡as¡¡we¡¡know£»¡¡and¡¡the¡¡mountains£»¡¡plains£»¡¡and
waters¡¡would¡¡foreshadow¡¡the¡¡salient¡¡features¡¡of¡¡our¡¡present¡¡land
and¡¡water¡£¡¡This¡¡view¡¡was¡¡held¡¡more¡¡or¡¡less¡¡distinctly£»¡¡sometimes
combined¡¡with¡¡the¡¡notion¡¡of¡¡recurrent¡¡cycles¡¡of¡¡change£»¡¡in
ancient¡¡times£»¡¡and¡¡its¡¡influence¡¡has¡¡been¡¡felt¡¡down¡¡to¡¡the
present¡¡day¡£¡¡It¡¡is¡¡worthy¡¡of¡¡remark¡¡that¡¡it¡¡is¡¡a¡¡hypothesis
which¡¡is¡¡not¡¡inconsistent¡¡with¡¡the¡¡doctrine¡¡of
Uniformitarianism£»¡¡with¡¡which¡¡geologists¡¡are¡¡familiar¡£
That¡¡doctrine¡¡was¡¡held¡¡by¡¡Hutton£»¡¡and¡¡in¡¡his¡¡earlier¡¡days¡¡by
Lyell¡£¡¡Hutton¡¡was¡¡struck¡¡by¡¡the¡¡demonstration¡¡of¡¡astronomers
that¡¡the¡¡perturbations¡¡of¡¡the¡¡planetary¡¡bodies£»¡¡however¡¡great
they¡¡may¡¡be£»¡¡yet¡¡sooner¡¡or¡¡later¡¡right¡¡themselves£»¡¡and¡¡that¡¡the
solar¡¡system¡¡possesses¡¡a¡¡self¡adjusting¡¡power¡¡by¡¡which¡¡these
aberrations¡¡are¡¡all¡¡brought¡¡back¡¡to¡¡a¡¡mean¡¡condition¡£
Hutton¡¡imagined¡¡that¡¡the¡¡like¡¡might¡¡be¡¡true¡¡of¡¡terrestrial
changes£»¡¡although¡¡no¡¡one¡¡recognised¡¡more¡¡clearly¡¡than¡¡he¡¡the
fact¡¡that¡¡the¡¡dry¡¡land¡¡is¡¡being¡¡constantly¡¡washed¡¡down¡¡by¡¡rain
and¡¡rivers¡¡and¡¡deposited¡¡in¡¡the¡¡sea£»¡¡and¡¡that¡¡thus£»¡¡in¡¡a¡¡longer
or¡¡shorter¡¡time£»¡¡the¡¡inequalities¡¡of¡¡the¡¡earth's¡¡surface¡¡must¡¡be
levelled£»¡¡and¡¡its¡¡high¡¡lands¡¡brought¡¡down¡¡to¡¡the¡¡ocean¡£
But£»¡¡taking¡¡into¡¡account¡¡the¡¡internal¡¡forces¡¡of¡¡the¡¡earth£»
which£»¡¡upheaving¡¡the¡¡sea¡bottom¡¡give¡¡rise¡¡to¡¡new¡¡land£»¡¡he
thought¡¡that¡¡these¡¡operations¡¡of¡¡degradation¡¡and¡¡elevation¡¡might
compensate¡¡each¡¡other£»¡¡and¡¡that¡¡thus£»¡¡for¡¡any¡¡assignable¡¡time£»
the¡¡general¡¡features¡¡of¡¡our¡¡planet¡¡might¡¡remain¡¡what¡¡they¡¡are¡£
And¡¡inasmuch¡¡as£»¡¡under¡¡these¡¡circumstances£»¡¡there¡¡need¡¡be¡¡no
limit¡¡to¡¡the¡¡propagation¡¡of¡¡animals¡¡and¡¡plants£»¡¡it¡¡is¡¡clear¡¡that
the¡¡consistent¡¡working¡¡out¡¡of¡¡the¡¡uniformitarian¡¡idea¡¡might¡¡lead
to¡¡the¡¡conception¡¡of¡¡the¡¡eternity¡¡of¡¡the¡¡world¡£¡¡Not¡¡that¡¡I¡¡mean
to¡¡say¡¡that¡¡either¡¡Hutton¡¡or¡¡Lyell¡¡held¡¡this¡¡conception
assuredly¡¡not£»¡¡they¡¡would¡¡have¡¡been¡¡the¡¡first¡¡to¡¡repudiate¡¡it¡£
Nevertheless£»¡¡the¡¡logical¡¡development¡¡of¡¡some¡¡of¡¡their¡¡arguments
tends¡¡directly¡¡towards¡¡this¡¡hypothesis¡£
The¡¡second¡¡hypothesis¡¡supposes¡¡that¡¡the¡¡present¡¡order¡¡of¡¡things£»
at¡¡some¡¡no¡¡very¡¡remote¡¡time£»¡¡had¡¡a¡¡sudden¡¡origin£»¡¡and¡¡that¡¡the
world£»¡¡such¡¡as¡¡it¡¡now¡¡is£»¡¡had¡¡chaos¡¡for¡¡its¡¡phenomenal
antecedent¡£¡¡That¡¡is¡¡the¡¡doctrine¡¡which¡¡you¡¡will¡¡find¡¡stated¡¡most
fully¡¡and¡¡clearly¡¡in¡¡the¡¡immortal¡¡poem¡¡of¡¡John¡¡Miltonthe
English¡¡Divina¡¡Commedia¡¡¡¨Paradise¡¡Lost¡£¡¨¡¡I¡¡believe¡¡it
is¡¡largely¡¡to¡¡the¡¡influence¡¡of¡¡that¡¡remarkable¡¡work£»¡¡combined
with¡¡the¡¡daily¡¡teachings¡¡to¡¡which¡¡we¡¡have¡¡all¡¡listened¡¡in¡¡our
childhood£»¡¡that¡¡this¡¡hypothesis¡¡owes¡¡its¡¡general¡¡wide¡¡diffusion
as¡¡one¡¡of
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