— 548 —
Thirdly, Of other Relations it is not easy to say how far.
      §18. As to the third sort of our Knowledge, viz. the Agreement or
Disagreement of any of our Ideas in any other Relation: This, as it is the
largest Field of our Knowledge, so it is hard to determine how far it
may extend: Because the Advances that are made in this part of
Knowledge, depending on our Sagacity, in finding intermediate
Ideas, that may shew the Relations and Habitudes of Ideas, whose Co-
existence is not considered, ’tis a hard Matter to tell, when we are
— 549 —
at an end of such Discoveries; and when Reason has all the helps it
is capable of, for the finding of Proofs, or examining the Agreement
or Disagreement of remote Ideas. They that are ignorant of Algebra
cannot imagine the Wonders in this kind are to be done by it: and
what farther Improvements and Helps, advantageous to other parts
of Knowledge, the sagacious Mind of Man may yet find out, ’tis not
easy to determine. This at least I believe, that the Ideas of Quantity
are not those alone that are capable of Demonstration and Knowledge;
and that other, and perhaps more useful parts of Contemplation,
would afford us Certainty, if Vices, Passions, and domineering Inter-
est did not oppose, or menace such Endeavours.
Morality capable of Demonstration.
      The Idea of a supreme Being, infinite in Power, Goodness, and
Wisdom, whose Workmanship we are, and on whom we depend;
and the Idea of our selves, as understanding, rational Beings, being
such as are clear in us, would, I suppose, if duly considered, and
pursued, afford such Foundations of our Duty and Rules of Action,
as might place Morality amongst the Sciences capable of Demonstration:
wherein I doubt not, but from self-evident Propositions, by neces-
sary Consequences, as incontestable as those in Mathematicks, the
measures of right and wrong might be made out, to any one that
will apply himself with the same Indifferency and Attention to the
one, as he does to the other of these Sciences. The Relation of other
Modes may certainly be perceived, as well as those of Number and
Extension: and I cannot see, why they should not also be capable of
Demonstration, if due Methods were thought on to examine, or
pursue their Agreement or Disagreement. Where there is no Property,
there is no Injustice, is a Proposition as certain as any Demonstration
in Euclid: For the Idea of Property, being a right to any thing; and
the Idea to which the Name Injustice is given, being the Invasion or
Violation of that right; it is evident, that these Ideas being thus
established, and these Names annexed to them, I can as certainly
know this Proposition to be true, as that a Triangle has three
— 550 —
Angles equal to two right ones. Again, No Government allows absolute
Liberty: The Idea of Government being the establishment of Society
upon certain Rules or Laws, which require Conformity to them;
and the Idea of absolute Liberty being for any one to do whatever
he pleases; I am as capable of being certain of the Truth of this
Proposition, as of any in Mathematicks.
Locke Hum IV, 3, §18, pp. 548-549-550