Etymology
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reasoning (n.)

late 14c., resouning, "exercise of the power of reason; act or process of thinking logically;" also an instance of this, a presentation of reasons or arguments; verbal noun from reason (v.).

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ratiocination (n.)

"process of reasoning, mental process of passing from the cognition of premises to the cognition of the conclusion," 1520s, from Latin ratiocinationem (nominative ratiocinatio) "a reasoning, calm reasoning," noun of action from past-participle stem of ratiocinari "to reckon, compute, calculate; to deliberate, meditate; to reason, argue, infer." This is a compound of ratio "reckoning, calculation," also "judgment, reason" (see ratio) + -cinari, which probably is related to conari "to endeavor, to try," from PIE *kona-, from root *ken- "to hasten, set oneself in motion" (see deacon).

Most writers make ratiocination synonymous with reasoning. J.S. Mill and others hold that the word is usually limited to necessary reasoning. [Century Dictionary]
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sophistry (n.)
"specious but fallacious reasoning," mid-14c., from Old French sophistrie (Modern French sophisterie), from Medieval Latin sophistria, from Latin sophista, sophistes (see sophist). "Sophistry applies to reasoning as sophism to a single argument" [Century Dictionary].
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blindly (adv.)
"in a blind manner; without sight; without reasoning," Old English blindlice; see blind (adj.) + -ly (2).
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argument (n.)
early 14c., "statements and reasoning in support of a proposition or causing belief in a doubtful matter," from Old French arguement "reasoning, opinion; accusation, charge" (13c.), from Latin argumentum "a logical argument; evidence, ground, support, proof," from arguere "make clear, make known, prove" (see argue). Sense passed through "subject of contention" (1590s) to "a quarrel" (by 1911), a sense formerly attached to argumentation.
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logic (n.)

mid-14c., logike, "branch of philosophy that treats of forms of thinking; the science of distinction of true from false reasoning," from Old French logique (13c.), from Latin (ars) logica "logic," from Greek (he) logike (techne) "(the) reasoning (art)," from fem. of logikos "pertaining to speaking or reasoning" (also "of or pertaining to speech"), from logos "reason, idea, word" (see Logos). Formerly also logick. Sometimes formerly plural, as in ethics, but this is not usual. Meaning "logical argumentation" is from c. 1600. Contemptuous logic-chopper "sophist, person who uses subtle distinctions in argument" is from 1846.

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illogical (adj.)
"without sound reasoning according to rules of logic," 1580s, from assimilated form of in- (1) "not, opposite of" + logical. Related: Illogically.
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dialectic (adj.)

1640s, "relating to the art of reasoning about probabilities," from Latin dialecticus, from Greek dialektikos "of conversation, discourse," from dialektos "discourse, conversation" (see dialect). From 1813 as "of or pertaining to a dialect or dialects." 

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discourse (n.)
Origin and meaning of discourse

late 14c., "process of understanding, reasoning, thought," from French discours, from Latin discursus "a running about," in Late Latin "conversation," in Medieval Latin "reasoning," noun use of past participle of discurrere "to run about, run to and fro, hasten," in Late Latin "to go over a subject, speak at length of, discourse of," from dis- "apart" (see dis-) + currere "to run" (from PIE root *kers- "to run").

Meaning "a running over a subject in speech, communication of thought in words" is from 1550s; sense of "discussion or treatment of a subject in formal speech or writing," is from 1580s.

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psittacism (n.)

"mere parroting, parrotry, repetition without reasoning," 1861, from French psittacisme (Liebnitz, 1765) or else from German psittazismus, both from Latin psittacus "parrot" (see psittacine) + -ism.

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