A scholar or theorist of ontology, or an adherent of a particular ontological doctrine.(noun)
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Use "ontologist" in a sentence
"A more boring possibility: 'ontologist' is a recognized specialization within that queen of sciences, library science."
"In The New York Times Book Review, the British pale-ontologist Simon Conway Morris threw down the gauntlet: he accused Wright "of a failure of nerve.""
"An ontologist might treat the same sort of ailments a psychiatrist would treat, but maybe rejects the latter's unquestioned belief in such a thing as a psyche."