The Collaborative International Dictionary of English v.0.48:

Reason \Rea"son\ (r[=e]"z'n), v. i. [imp. & p. p. Reasoned
   (r[=e]"z'nd); p. pr. & vb. n. Reasoning.] [Cf. F.
   raisonner. See Reason, n.]
   1. 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.
      [1913 Webster]

   2. Hence: To carry on a process of deduction or of induction,
      in order to convince or to confute; to formulate and set
      forth propositions and the inferences from them; to argue.
      [1913 Webster]

            Stand still, that I may reason with you, before the
            Lord, of all the righteous acts of the Lord. --1
                                                  Sam. xii. 7.
      [1913 Webster]

   3. To converse; to compare opinions. --Shak.
      [1913 Webster]

WordNet (r) 3.0 (2006):

reasoned
    adj 1: logically valid; "a sound argument" [syn: reasoned,
           sound, well-grounded]