ot only the
same outward shape, but the same inward constitution, which, therefore,
may be called the Form of apple-stuff itself--namely, a certain
pulpiness, juiciness, sweetness, etc.; qualities common to all dessert
apples: yet their Matter is different, one being here, another
there--differing in place or time, if in nothing else. The definition of
a species is the form of every specimen of it.

To apply this distinction to the things of Logic: it is easy to see how
two propositions may have the same Form but different Matter: not using
'Form' in the sense of 'shape,' but for that which is common to many
things, in contrast with that which is peculiar to each. Thus, _All male
lions are tawny_ and _All water is liquid at 50 deg. Fahrenheit_, are two
propositions that have the same form, though their matter is entirely
different. They both predicate something of the whole of their subjects,
though their subjects are different, and so are the things predicated of
them. Again, _All male lions have tufted tails_ and _All male lions have
manes_, are two propositions having the same form and, in their
subjects, the same matter, but different matter in their predicates. If,
however, we take two such propositions as these: _All male lions have
manes_ and _Some male lions have manes_, here the matter is the same in
both, but the form is different--in the first, predication is made
concerning _every_ male lion; in the second of only _some_ male lions;
the first is _universal_, the second is _particular_. Or, again, if we
take _Some tigers are man-eaters_ and _Some tigers are not man-eaters_,
here too the matter is the same, but the form is different; for the
first proposition is _affirmative_, whilst the second is _negative_.

Sec. 6. Now, according to Hamilton and Whately, pure Logic has to do only
with the Form of propositions and arguments. As to their Matter, whether
they are really true in fact, that is a question, they said, not for
Logic, but for experience, or for the special sciences. But Mill desired
so to extend logical method as to test the material truth of
propositions: he thought that he could expound a method by which
experience itself and the conclusions of the special sciences may be
examined.

To this method it may be objected, that the claim to determine Material
Truth takes for granted that the order of Nature will remain unchanged,
that (for example) water not only at present is a liquid at 50 deg.
Fah