positivism has 3 distinct synonyms spread across 2 of its 2 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 form of empiricism that bases all knowledge on perceptual experience (not on intuition or revelation)
a quality or state characterized by certainty or acceptance or affirmation and dogmatic assertiveness
Synonyms, antonyms and the broader and narrower relations for positivism come from Princeton University’s WordNet. Full sources and licences.