Source : Webster's Revised Unabridged Dictionary (1913)

Ratiocination \Ra`ti*oc"i*na"tion\, n. [L. ratiocinatio: cf. F.
   ratiocination.]
   The process of reasoning, or deducing conclusions from
   premises; deductive reasoning.

Source : WordNet®

ratiocination
     n 1: the proposition arrived at by logical reasoning (such as the
          proposition that must follow from the major and minor
          premises of a syllogism) [syn: {conclusion}]
     2: logical and methodical reasoning