ntirely from
confusing a transitory imperfection with an essential character. So long
as our information concerning them is imperfect, we class all objects
together according to resemblances which we _feel_, but cannot _define_:
we group them round _types_, in short. Thus, if you ask an ordinary
person what kinds of animals there are, he will probably say, beasts,
birds, reptiles, fishes, insects, &c. Ask him to define a beast from a
reptile, and he cannot do it; but he says, things like a cow or a horse
are beasts, and things like a frog or a lizard are reptiles. You see _he
does_ class by type, and not by definition. But how does this
classification differ from that of the scientific Zoologist? How does
the meaning of the scientific class-name of "Mammalia" differ from the
unscientific of "Beasts"?

Why, exactly because the former depends on a definition, the latter on a
type. The class Mammalia is scientifically defined as "all animals which
have a vertebrated skeleton and suckle their young." Here is no
reference to type, but a definition rigorous enough for a geometrician.
And such is the character which every scientific naturalist recognises
as that to which his classes must aspire--knowing, as he does, that
classification by type is simply an acknowledgment of ignorance and a
temporary device.

So much in the way of negative argument as against the reputed
differences, between Biological and other methods. No such differences,
I believe, really exist. The subject-matter of Biological science is
different from that of other sciences, but the methods of all are
identical; and these methods are--

1. _Observation_ of facts--including under this head that _artificial
observation_ which is called _experiment_.

2. That process of tying up similar facts into bundles, ticketed and
ready for use, which is called _Comparison_ and _Classification_,--the
results of the process, the ticketed bundles, being named _General
propositions_.

3. _Deduction_, which takes us from the general proposition to facts
again--teaches us, if I may so say, to anticipate from the ticket what
is inside the bundle. And finally--

4. _Verification_, which is the process of ascertaining whether, in
point of fact, our anticipation is a correct one.

Such are the methods of all science whatsoever; but perhaps you will
permit me to give you an illustration of their employment in the science
of Life; and I will take as a special case, the es