In logic, an argumentum e contrario, also known as appeal from the contrary, denotes any proposition that is argued to be correct because it is not disproven by a certain case. It is the opposite of the analogy. When analogy is allowed, e contrario is forbidden and vice versa. Arguments e contrario are often used in the legal system as a way to solve problems not currently covered by a certain system of laws. Although it might be used as a logical fallacy, arguments e contrario are not by definition fallacies.

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