the act or process of a person who reasons.

the process of forming conclusions, judgments, or inferences from facts or premises.

the reasons, arguments, proofs, etc., resulting from this process.

noun

irrationality , nonsense

noun

acumen , analysis , apriority , argument , case , cogitation , concluding , corollary , deduction , dialectics , exposition , generalization , hypothesis , illation , induction , inference , interpretation , logistics , premise , proof , proposition , ratiocination , rationale , rationalizing , reason , syllogism , syllogization , thinking , thought , train of thought , (sophistical or false) sophistry , argumentation , basis , casuistry , discursus , fallacy , logic