Source : Webster's Revised Unabridged Dictionary (1913)

Ratiocinative \Ra`ti*oc"i*na*tive\, a. [L. ratiocinativus.]
   Characterized by, or addicted to, ratiocination; consisting
   in the comparison of proportions or facts, and the deduction
   of inferences from the comparison; argumentative; as, a
   ratiocinative process.

         The ratiocinative meditativeness of his character.
                                                  --Coleridge.

Source : WordNet®

ratiocinative
     adj : based on exact thinking; "one's ratiocinative powers"