Click on the phrases to see them in context. The original texts by Immanuel Kant and David Hume are available from the Gutenberg Projet.
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In the former example, my perceptions in the apprehension of a house might begin at the roof and end at the foundation, or vice versa; or I might apprehend the manifold in this empirical intuition, by going from left to right, and from right to left. But to make the matter still more certain, I alter the object; and instead of vice and virtue, make the trial upon beauty and deformity, riches and poverty, power and servitude. It is impossible, therefore, that the character of natural and unnatural can ever, in any sense, mark the boundaries of vice and virtue.