logic has 2 distinct synonyms spread across 1 of its 5 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. WordNet records no antonym for it — antonymy is a relation between word forms rather than concepts, so it is deliberately sparse.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
the branch of philosophy that analyzes inference
reasoned and reasonable judgment
“it made a certain kind of logic”
the principles that guide reasoning within a given field or situation
“economic logic requires it”
the system of operations performed by a computer that underlies the machine's representation of logical operations
a system of reasoning
Synonyms, antonyms and the broader and narrower relations for logic come from Princeton University’s WordNet. Full sources and licences.