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, To converse; to compare opinions, To persuade or dissuade (someone) with reasons, noun_ A declaration made to explain or justify action, decision, or conviction, A fact or cause that explains why something exists or has occurred, The faculty by which we attain the knowledge of first principles; a faculty for apprehending the unconditioned