An introductory text-book of logic - Mellone, Sydney - Rare Books at ...

46
THE NAME, THE TERM, THE CONCEPT,
only must be true. The second and third laws give a
progressive unfolding of the implications
of the first.
14. Since the time of Leibniz an important principle
has been introduced in Logic and placed by the side
of the three laws of which we have spoken. It is called
the law or principle of Sufficient Reason, and is usually
stated thus :
"
For everything there is a sufficient reason
why it is so rather than otherwise." In this principle
two different laws of thought are brought together,
which must be distinguished, and, for the purposes of
elementary Logic, carefully separated.
(a) The first principle states that for every proposi
tion which is held to be true, there must be reasons for
regarding it as true, arguments which may be brought
in support of it. It must be capable of being shown
as the conclusion from certain premises. In other
words, every judgment, when questioned, expands into
an inference. This does not apply to the propositions
which state the
"
laws of
"
thought
cannot be
; they
proved by argument, from premises to conclusion,
they cannot be, in this sense, inferred ; for all argument
and all inference depends upon them.
The principle that every judgment justifies itself
by expanding into an inference, is really part
of a
wider principle, that all parts of our knowledge, so
far as they are true knowledge, are connected to
gether. We know that any statement, once admitted
to be true, may have a modifying effect upon any other
portion of our knowledge. All the current scientific,
theological, and philosophical controversies afford abun
dant illustrations of this fact ; and it is a fact, because
every judgment is at bottom connected with every
other one. We cannot show this connection, in many
cases ; but most of the controversies alluded to consist