Etymology
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ipse dixit 
Latin, literally "he (the master) said it," translation of Greek autos epha, phrase used by disciples of Pythagoras when quoting their master. Hence, "an assertion made without proof, resting entirely on the authority of the speaker" (1590s), ipsedixitism "practice of dogmatic assertion" (1830, Bentham), etc.
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ipso facto 
Latin adverbial phrase, literally "by that very fact, by the fact itself," from neuter ablative of ipse "he, himself, self" + ablative of factum "fact" (see fact).
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