1. (n.) A thought or a consideration offered in support of a determination or an opinion; a just ground for a conclusion or an action; that which is offered or accepted as an explanation; the efficient cause of an occurrence or a phenomenon; a motive for an action or a determination; proof, more or less decisive, for an opinion or a conclusion; principle; efficient cause; final cause; ground of argument.

2. (n.) The faculty or capacity of the human mind by which it is distinguished from the intelligence of the inferior animals; the higher as distinguished from the lower cognitive faculties, sense, imagination, and memory, and in contrast to the feelings and desires. Reason comprises conception, judgment, reasoning, and the intuitional faculty. Specifically, it is the intuitional faculty, or the faculty of first truths, as distinguished from the understanding, which is called the discursive or ratiocinative faculty.

3. (n.) Due exercise of the reasoning faculty; accordance with, or that which is accordant with and ratified by, the mind rightly exercised; right intellectual judgment; clear and fair deductions from true principles; that which is dictated or supported by the common sense of mankind; right conduct; right; propriety; justice.

4. (n.) Ratio; proportion.

5. (n.) To exercise the rational faculty; to deduce inferences from premises; to perform the process of deduction or of induction; to ratiocinate; to reach conclusions by a systematic comparison of facts.

6. (n.) Hence: To carry on a process of deduction or of induction, in order to convince or to confute; to formulate and set forth propositions and the inferences from them; to argue.

7. (n.) To converse; to compare opinions.

8. (v. t.) To arrange and present the reasons for or against; to examine or discuss by arguments; to debate or discuss; as, I reasoned the matter with my friend.

9. (v. t.) To support with reasons, as a request.

10. (v. t.) To persuade by reasoning or argument; as, to reason one into a belief; to reason one out of his plan.

11. (v. t.) To overcome or conquer by adducing reasons; -- with down; as, to reason down a passion.

12. (v. t.) To find by logical processes; to explain or justify by reason or argument; -- usually with out; as, to reason out the causes of the librations of the moon.

Vernunft acceptable accomplishment account admissibility advise with aim air allegorization ambition analyze answer antecedent apologia apology apply reason argument argumentum ascertainment aspiration balance bargain basis because of brain brains by reason of by virtue of calculate call call in calling canvass case cause cerebrate clarification clearing up cogitate collect collogue comment upon common sense compare notes conceive conception conceptualize conclude confer confer with cons consider consideration consult consult with contact with reality controvert convince cool head coolheadedness coolness counsel cracking deal with debate decipherment decoding deduce deduction deductive reasoning defence deliberate deliberate upon demonstration demythologization denouement derive determinant determination discourse discourse about discourse of reason discursive reason discuss discuss with disentanglement dissuade draw a conclusion draw an inference due sense of due to editing elenchus elucidation emendation end end result enlightenment entertain ideas esprit estimate euhemerism examine exchange observations exchange views excuse exegesis exemplification exercise the mind explanation explication exposition expounding extract fetch figure out find finding finding-out fitting form ideas foundation gather generalize glean go into goal good reason good sense gray matter ground grounds guiding light guiding star handle have conversations head headpiece healthy mind hold conference horse sense hypothesize ideal ideate ignoratio elenchi illumination illustration induce induction inductive reasoning infer inference insight inspiration intellect intellection intellectual faculty intellectualize intelligence intention interpretation investigate issue judgement justifiability justifiable justification justness knock around level head levelheadedness light lodestar logic logical thought logicality logicalize logicalness logicize lucid interval lucidity mainspring marbles material basis matter mens mental balance mental capacity mental equilibrium mental health mental hygiene mental poise mentality mind motive negotiate normalcy normality normalness nous object objective occasion on account of outcome owing to palaver parley pass under review percipience perspicacity persuade philosophize philosophy plaidoyer plain sense plausibility plea plead with pleading point power of reason powwow practical mind practical wisdom practicality pretense pretext prevail upon principle proof proper pros pros and cons provide a rationale psyche purpose put heads together rap ratio ratiocination rational rational ground rationale rationalism rationality rationalization rationalize rationalizing reason about reason for reason that reason the point reason why