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.
Fahrenheit, but will always be so; whereas (although we have no reason to expect such a thing) the order of Nature may alter--it is at least supposable--and in that event water may freeze at such a temperature.
Any matter of fact, again, must depend on observation, either directly, or by inference--as when something is asserted about atoms or ether.