Which of these rhetorical devices does thoreau use here

D. Metaphor.

Explanation:

The use of a metaphor as a persuasive strategy has had a recurrence in contemporary political communication and constitutes a clear example of the influence that the discourse exerts on the representations of the elector and on what has been called "public opinion". In this extract the speech alludes to two books famous for being full of wisdom and that are know to get, or at least try to define, the best in human behavior possible.

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