— 609 —
As First, Identical Propositions.
      §2. First, All purely identical Propositions. These obviously, and at
first blush, appear to contain no Instruction in them. For when we
affirm the same Term of it self, whether it be barely verbal, or
whether it contains any clear and real Idea, it shews us nothing,
but what we must certainly know before, whether such a Proposi-
tion be either made by, or proposed to us. Indeed, that most general
one, What is, is, may serve sometimes to shew a Man the absurdity
he is guilty of, when by circumlocution, or equivocal terms, he
would, in particular Instances, deny the same thing of it self;
because no body will so openly bid defiance to common Sense, as to
affirm visible and direct Contradictions in plain Words: Or if he
does, a Man is excused if he breaks off any farther Discourse with
him. But yet, I think, I may say, that neither that received Maxim,
nor any other identical Proposition teaches us any thing: And
though in such kind of Propositions, this great and magnified
Maxim, boasted to be the foundation of Demonstration, may be, and
often is made use of to confirm them, yet all it proves, amounts to
no more than this, That the same Word may with great certainty
be affirmed of it self, without any doubt of the Truth of any such
Proposition;
Locke Hum IV, 8, §2, p. 609