here too the matter is the same, but the form is different; for the
first proposition is _affirmative_, whilst the second is _negative_.

§ 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°
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. But
observation and material inference are subject to the limitations of our
faculties; and however we may aid observation by microscopes and
micrometers, it is still observation; and however we may correct our
observations by repetition, comparison and refined mathematical methods
of making allowances, the correction of error is only an approximation
to accuracy. Outside of Formal Reasoning, suspense of judgment is your
only attitude.

But such objections imply that nothing short of absolute truth has any
value; that all our discussions and investigations in science or social