irrationality in thought or action.
an attitude or belief having a nonrational basis.
a theory that nonrational forces govern the universe.

1805–15; irrational + -ism

irrationalist, adjective, noun
irrationalistic, adjective Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
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World English Dictionary
irrationality or irrationalism (ɪˌræʃəˈnælɪtɪ)
1.  the state or quality of being irrational
2.  irrational thought, action, or behaviour
irrationalism or irrationalism

Collins English Dictionary - Complete & Unabridged 10th Edition
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Encyclopedia Britannica


a 19th- and early 20th-century philosophical trend that claimed to enrich man's apprehension of life by expanding it beyond the rational to its fuller dimensions. Rooted either in metaphysics or in an awareness of the uniqueness of human experience, irrationalism stressed the dimensions of instinct, feeling, and will as over and against reason. The term is used chiefly by continental European philosophers, who regard irrationalism as one of several strong currents flowing into the 20th century.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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Example sentences
It accomplishes nothing with the militants but exposes their irrationalism to the lurkers.
The war of ideas is a war about rationalism as opposed to irrationalism.
To be specific, you speak of a belief in a soul as either a misunderstanding of science, or some form of chosen irrationalism.
To be sure, there is plenty of evidence that ignorance and irrationalism are rampant.
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