2 ON THE CLASSIFICATION OF BIRDS. 
we are bound to make good, as best we can, in the ae 
tails of all its classes and prominent groups: we are, in 
short, to bring our theory into practice, and — so far as 
our limited knowledge will permit—to substantiate this — 
theory by analysis. If we fail in this, —if, ina group 
confessedly natural, our theory disturbs and disarranges 
the evident series of nature, or fails to explain the prin- 
ciples of its minor variations, — we are quite willing it 
should be received with doubt and distrust. Or if our 
opponents, by any theory of their own, equally compre- 
hensive, can explain and illustrate what this cannot do, 
we will then not only consent to abandon our propos- 
itions as untenable, but adopt any other nfore demon- 
strative of the unity of Nature’s laws. Until this, how- 
ever, is done, or until something more philosophic is urged 
against us than the old reiterated assertion that “‘ the time 
has not yet come”’* for these investigations, &c. &c., we 
may be allowed to preserve silence: these vague and 
querulous complaints, in truth, have emanated from 
those only who have hitherto done nothing to place their 
names in the prominent ranks of science, and who may 
consequently be presumed inadequate judges upon mat- 
ters they have not sufficiently studied. We may be 
allowed to remind such objectors, as well as to urge . 
upon all naturalists, that it is both unphilosophic and un- 
fair to pronounce upon the value of any theory, until 
the whole of the facts intended to prove its truth are 
laid before them. We have, in the onset, clearly stated 
our propositions, and declared that our proofs would fol- 
low, as we successively brought under examination every 
class of the animal kingdom. When the whole of these 
are gone through, and the Capinet or Natura His- 
ToRY is completed, it will then be the proper time to de- 
termine whether our views of the general laws of nature 
are erroneous, whether we have not sufficient facts 
before us, or "whether we are to wait, as these writers 
insinuate, (perhaps another century) until our knowledge 
of natural objects —almost overwhelming as it now is— 
* Magazine of Zoology and Botany, i. p. 20; &c. 
“Ss 
