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able to judge of any considerable number. Fewer still are 
competent to pronounce upon the relation of each part to every 
other, and the cumulative force of all as they bear upon the 
grand conclusion. What is within the sphere of each man's 
specialty he can understand. What is derived from the sphere 
of another's observation or thought he must take in some 
sense upon trust. The general similarity between the several 
relations and facts of the several spheres any man can vaguely 
appreciate, and hence the generalizations of the theory seem 
plausible at their first impression, though the impression is 
vague, and perhaps because it is vague. Meanwhile the con- 
fiding student trusts to the brilliant suggestions of the con- 
fident theorist and his more confident asseverations. So long 
as he is in the attitude of a learner, the path is easy ; but so 
soon as he is summoned to the duty of the critic his task is 
difficult and irksome, because he must of necessity pass judg- 
ment upon subject-matters with which he is not familiar, and 
in respect to which he feels that he is incompetent to act as a 
judge. That many physiologists should favour a system of 
philosophy which finds development everywhere is not very 
surprising. That those who are not physiologists in special 
should at first hesitate, and know not what to say, and then be 
dazed by the imposing plausibility of the generalizations which 
they cannot fully appreciate, and finally relapse into a “ silence 
which is taken for consent," seems at first thought surprising, 
but on second thought is altogether natural. Explain the fact 
as we may, the theory takes captive many a general student 
and otherwise critical thinker simply because he is unable to 
reply to the reasonings on many points which are out of the 
range of his studies. And yet the breadth of the generalizations, 
the confidence with which they are urged, the nonchalance with 
which difficulties are surmounted, the vast number of facts 
which the expounder has at his command, the ease with which 
he marshals them under groups, and, above all, the mysterious 
fascination with which the phenomena of growth and change 
are invested to every imaginative mind — all these account, in 
part, for the unquestioning acceptance of the theory by many 
quick-minded thinkers who would confess themselves alto- 
gether disqualified closely to scrutinize its claims. It is obvious 
that those who, for the reasons given, cannot understand the 
arguments for, are disqualified to understand the arguments 
against, and hence special and minute criticisms of these 
pretentious and portentous theories attract attention from but 
few. 
There is one line of argument, however, which is accessible 
to every mind. It concerns itself with the relation of this 
