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And general Propositions concerning abstract Ideas.
      §14. In the former case, our Knowledge is the consequence of the
Existence of Things producing Ideas in our Minds by our Senses: in
the latter, Knowledge is the consequence of the Ideas (be they what
they will) that are in our Minds producing there general certain
Propositions. Many of these are called aeternae veritates, and all of
them indeed are so; not from being written all or any of them in the
Minds of all Men, or that they were any of them Propositions in any
ones Mind, till he, having got the abstract Ideas, joyn’d or separated
them by affirmation or negation. But wheresoever we can suppose
such a creature as Man is, endowed with such faculties, and thereby
furnished with such Ideas, as we have, we must conclude, he must
needs, when he applies his thoughts to the consideration of his
Ideas, know the truth of certain Propositions, that will arise from the
Agreement or Disagreement, which he will perceive in his own
Ideas. Such Propositions are therefore called Eternal Truths, not
because they are Eternal Propositions actually formed, and ante-
cedent to the Understanding, that at any time makes them; nor
because they are imprinted on the Mind from any patterns, that
— 639 —
are any where of them out of the Mind, and existed before: But
because being once made, about abstract Ideas, so as to be true, they
will, whenever they can be supposed to be made again at any time
past or to come, by a Mind having those Ideas, always actually be
true. For Names being supposed to stand perpetually for the same
Ideas; and the same Ideas having immutably the same Habitudes
one to another, Propositions, concerning any abstract Ideas, that
are once true, must needs be eternal Verities.
Locke Hum IV, 11, §14, pp. 638-639