Page:An Enquiry Concerning Human Understanding - Hume (1748).djvu/111



great Advantage of the mathematical Sciences above the moral consists in this, that the Ideas of the former, being sensible, are always clear and determinate, the smallest Distinction betwixt them is immediately perceptible, and the same Terms are still expressive of the same Ideas, without Ambiguity or Variation. An Oval is never mistaken for a Circle, nor an Hyperbola for an Ellipsis. The Isoceles and Scalenum are distinguish'd by Boundaries more exact than Vice and Virtue, Right and Wrong. If any Term be defin'd in Geometry, the Mind readily, of itself, substitutes, on all Occasions, the Definition for the Term defin'd: Or even when no Definition is