reasoning (n.)

c. 1400, resounen, "to question (someone)," also "to challenge," from Old French resoner, raisoner "speak, discuss; argue; address; speak to," from Late Latin rationare "to discourse," from Latin ratio "reckoning, understanding, motive, cause," from ratus, past participle of reri "to reckon, think" (from PIE root *re- "to reason, count").

The intransitive sense of "to think in a logical manner, exercise the faculty of reason" is from 1590s; transitive sense of "employ reasoning (with someone)" is from 1680s. Related: Reasoned; reasoning.