3. Demonstration depends on clearly perceived proofs.
Those intervening ideas, which serve to show the
agreement of any two others, are called proofs; and where the agreement and disagreement is by this means
plainly and clearly perceived, it is called demonstration; it being shown to the understanding, and the mind made
to see that it is so. A quickness in the mind to find out these intermediate ideas, (that shall discover the agreement
or disagreement of any other,) and to apply them right, is, I suppose, that which is called sagacity.
