bjects themselves. The
argument on which these views are founded may be summed up in the
following few words: Species, genera, families, etc., exist as
thoughts, individuals as facts."[11]

An ingenious dilemma caps the argument:--

"It seems to me that there is much confusion of ideas in the general
statement of the variability of species so often repeated lately. If
species do not exist at all, as the supporters of the transmutation
theory maintain, how can they vary? and if individuals alone exist,
how can the differences which may be observed among them prove the
variability of species?"

Now we imagine that Mr. Darwin need not be dangerously gored by either
horn of this curious dilemma. Although we ourselves cherish
old-fashioned prejudices in favor of the probable permanence, and
therefore of a more stable objective ground of species, yet we
agree--and Mr. Darwin will agree fully with Mr. Agassiz--that species,
and he will add varieties, "exist as categories of thought," that is,
as cognizable distinctions,--which is all that we can make of the
phrase here, whatever it may mean in the Aristotelian metaphysics.
Admitting that species are only categories of thought, and not facts
or things, how does this prevent the individuals, which are material
things, from having varied in the course of time, so as to exemplify
the present almost innumerable categories of thought, or embodiments
of Divine thoughts in material forms, or--viewed on the human side--in
forms marked with such orderly and graduated resemblances and
differences as to suggest to our minds the idea of species, genera,
orders, etc., and to our reason the inference of a Divine original? We
have no clear idea how Mr. Agassiz intends to answer this question, in
saying that branches are founded upon different plans of structure,
classes upon different modes of execution of these plans, orders on
different degrees of complication in the mode of execution, families
upon different patterns of form, genera upon ultimate peculiarities of
structure, and species upon relations and proportions. That is, we do
not perceive how these several "categories of thought" exclude the
possibility or the probability that the individuals which manifest or
suggest the thoughts had an ultimate community of origin. Moreover,
Mr. Darwin would insinuate that the particular philosophy of
classification upon which this whole argument reposes is as purely
hypothetical and as little