Ideas in mathematics are a sure ground of certainty; and yet everyone may not make so right an use of them, as to attain to certainty by them: but yet anyone's failing of certainty by them, is not the overturning of this truth, that certainty is to be had by them.

The Works of John Locke, A Letter to the Right Rev. Edward Lord Bishop of Worcester (p. 56), Printed for Thomas Tegg. 1823