— 532 —
Depends on Proofs.
      §3. Those intervening Ideas, which serve to shew the Agreement
of any two others, are called Proofs; and where the Agreement or
Disagreement is by this means plainly and clearly perceived, it is
called Demonstration, it being shewn to the Understanding, and the
Mind made 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.
Locke Hum IV, 2, §3, p. 532