"Cunning has only private selfish aims, and sticks at nothing which may make them succeed. Discretion has large and extended views, and, like a well-formed eye, commands a whole horizon; cunning is a kind of shortsightedness, that discovers the minutest objects which are near at hand, but is not able to discern things at a distance."

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There are, then, these three means of effecting persuasion. The man who is to be in command of them must, it is clear, be able (1) to reason logically, (2) to understand human character and goodness in their various forms, and (3) to understand the emotions--that is, to name them and describe them, to know their causes and the way in which they are excited.

— Aristotle