charles_darwin

128
Primary Documents Relating to Darwin and Darwinism
grasp both the causes of the progress and of the interruptions
in it.
When once we have recognised that a thing is useful and
indeed indispensable for the end in view and that it is free from
drawbacks, we should hasten to carry it into execution although
it is contrary to custom.
This is the case with regard to the way in which a general
classification of animals should be drawn up.
We shall see that it is not a matter of indifference from
which end we begin this general classification of animals, and
that the beginning of the order is not a mere matter of choice.
The existing custom of placing at the head of the animal
kingdom the most perfect animals, and of terminating this kingdom
with the most imperfect and simplest in organisation, is due,
on the one hand, to that natural prejudice towards giving the
preference to the objects which strike us most or in which we are
most pleased or interested; and, on the other hand, to the preference
for passing from the better known to what is less known.
When the study of natural history began to occupy attention
these reasons were no doubt very plausible; but they must
now yield to the needs of science and especially to those facilitating
the progress of natural knowledge.
With regard to the numerous and varied animals which nature
has produced, if we cannot flatter ourselves that we possess
an exact knowledge of the real order which she followed in
bringing them successively into existence, it is nevertheless true
that the order which I am about to set forth is probably very
near it: reason and all our acquired knowledge testify in favour
of this probability.
If indeed it is true that all living bodies are productions of
nature, we are driven to the belief that she can only have produced
them one after another and not all in a moment. Now if
she shaped them one after another, there are grounds for thinking
that she began exclusively with the simplest, and only produced
at the very end the most complex organisations both of
the animal and vegetable kingdoms.
To assist us to a judgment as to whether the idea of species
has any real foundations, let us revert to the principles already
set forth; they show:
(1) That all the organised bodies of our earth are true
productions of nature, wrought successively throughout long
periods of time.
(2) That in her procedure, nature began and still begins by
fashioning the simplest of organised bodies, and that it is these
alone which she fashions immediately, that is to say, only the
rudiments of organisation indicated in the term spontaneous
generation.