Word Study
Contraries (root: contrary)
CIDE DICTIONARY
Propositions which directly and destructively contradict each other, but of which the falsehood of one does not establish the truth of the other. [1913 Webster]
"If two universals differ in quality, they are contraries; as, every vine is a tree; no vine is a tree. These can never be both true together; but they may be both false." [1913 Webster]
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