One who is irrational in their beliefs or ideas.(noun)
Someone who rejects some aspect of rationalism.(noun)
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Use "irrationalist" in a sentence
"I'm not sure whether the old irrationalist would have welcomed this himself, or not."
"We need to adopt a scientific approach to things because the hour is getting very late to be able to indulge in having key decisions made by religious people; by irrationalist by those who will steer the ship by faith and not by a compass but by the equal of reading the entrails of a chicken."
"It is not and should never be, as has happened with the irrationalist, pseudo-scientific, anti-metaphysical, socialist left who control all modes of political thought in intellectual ‘debate’ these days, a method of creating a new God who actively attempts to snuff out divergent and opposed opinion."