Question

which figure of speech is used in this text?
i know that i know nothing.
—attributed to socrates

euphemism
paradox
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Explanation:

A paradox is a statement that seems self-contradictory but may hold a deeper truth. The phrase "I know that I know nothing" presents an apparent contradiction (claiming knowledge of one's own lack of knowledge), which fits the definition of a paradox. A euphemism is a mild term replacing an offensive one, which does not apply here.

Answer:

paradox