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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 patience and
faithfulness with which the investigator applies to his hypothesis
every possible kind of verification。
ON THE PHYSICAL BASIS OF LIFE ＇92＇
In order to make the title of this discourse generally
intelligible； I have translated the term 〃Protoplasm；〃 which is the
scientific name of the substance of which I am about to speak； by
the words 〃the physical basis of life。〃 I suppose that； to many；
the idea that there is such a thing as a physical basis； or matter；
of life may be novelso widely spread is the conception of life as
a something which works through matter； but is independent of it；
and even those who are aware that matter and life are inseparably
connected； may not be prepared for the conclusion plainly suggested
by the phrase； 〃THE physical basis or matter of life；〃 that there
is some one kind of matter which is common to all living beings；
and that their endless diversities are bound together by a
physical； as well as an ideal； unity。 In fact； when first
apprehended； such a doctrine as this appears almost shocking to
common sense。
What； truly； can seem to be more obviously different from one
another； in faculty； in form； and in substance； than the various
kinds of living beings？ What community of faculty can there be
between the bright…coloured lichen； which so nearly resembles a
mere mineral incrustation of the bare rock on which it grows； and
the painter； to whom it is instinct with beauty； or the botanist；
whom it feeds with knowledge？
Again； think of the microscopic fungusa mere infinitesimal ovoid
particle； which finds space and duration enough to multiply into
countless millions in the body of a living fly； and then of the
wealth of foliage； the luxuriance of flower and fruit； which lies
between this bald sketch of a plant and the giant pine of
California； towering to the dimensions of a cathedral spire； or the
Indian fig； which covers acres with its profound shadow； and
endures while nations and empires come and go around its vast
circumference。 Or； turning to the other half of the world of life；
picture to yourselves the great Finner whale；＇93＇ hugest of beasts
that live； or have lived； disporting his eighty or ninety feet of bone；
muscle and blubber； with easy roll； among waves in which the
stoutest ship that ever left dockyard would flounder hopelessly；
and contrast him with the invisible animalculesmere gelatinous
specks； multitudes of which could； in fact； dance upon the point of
a needle with the same ease as the angels of the Schoolmen could；
in imagination。 With these images before your minds； you may well
ask； what community of form； or structure； is there between the
animalcule and the whale； or between the fungus and the fig…tree？
And； a fortiori；＇94＇ between all four？
Finally； if we regard substance； or material composition； what
hidden bond can connect the flower which a girl wears in her hair
and the blood which courses through her youthful veins； or； what is
there in common between the dense and resisting mass of the oak； or
the strong fabric of the tortoise； and those broad disks of glassy
jelly which may be seen pulsating through the waters of a calm sea；
but which drain away to mere films in the hand which raises them
out of their element？
Such objections as these must； I think； arise in the mind of every
one who ponders； for the first time； upon the conception of a
single physical basis of life underlying all the diversities of
vital existence； but I propose to demonstrate to you that；
notwithstanding these apparent difficulties； a threefold unity
namely； a unity of power or faculty； a unity of form； and a unity
of substantial compositiondoes pervade the whole living world。
No very abstruse argumentation is needed； in the first place to
prove that the powers； or faculties； of all kinds of living matter；
diverse as they may be in degree； are substantially similar in
kind。
Goethe has condensed a survey of all powers of mankind into the
well…known epigram：＇95＇
〃Warum treibt sich das Volk so und schreit？ Es will sich ernahren
Kinder zeugen； und die nahren so gut es vermag。
。 。 。 。 。 。 。 。 。 。 。 。 。
Weiter bringt es kein Mensch； stell' er sich wie er auch will。〃
In physiological language this means； that all the multifarious and
complicated activities of man are comprehensible under three
categories。 Either they are immediately directed towards the
maintenance and development of the body； or they effect transitory
changes in the relative positions of parts of the body； or they
tend towards the continuance of the species。 Even those
manifestations of intellect； of feeling； and of will； which we
rightly name the higher faculties； are not excluded from this
classification； inasmuch as to every one but the subject of them；
they are known only as transitory changes in the relative positions
of parts of the body。 Speech； gesture； and every other form of
human action are； in the long run； resolvable into muscular
contraction； and muscular contraction is but a transitory change in
the relative positions of the parts of a muscle。 But the scheme
which is large enough to embrace the activities of the highest form
of life； covers all those of the lower creatures。 The lowest
plant； or animalcule； feeds； grows； and reproduces its kind。 In
addition； all animals manifest those transitory changes of form
which we clas