The Collaborative International Dictionary of English v.0.48:

Rationality \Ra`tion*al"i*ty\ (r[a^]sh"[u^]n*[a^]l"[i^]*t[y^];
   277), n.; pl. -ties (-t[i^]z). [F. rationalit['e], or L.
   rationalitas.]
   The quality or state of being rational; agreement with
   reason; possession of reason; due exercise of reason;
   reasonableness.
   [1913 Webster]

         When God has made rationality the common portion of
         mankind, how came it to be thy inclosure? --Gov. of
                                                  Tongue.
   [1913 Webster]

         Well-directed intentions, whose rationalities will
         never bear a rigid examination.          --Sir T.
                                                  Browne.
   [1913 Webster]

WordNet (r) 3.0 (2006):

rationality
    n 1: the state of having good sense and sound judgment; "his
         rationality may have been impaired"; "he had to rely less
         on reason than on rousing their emotions" [syn:
         rationality, reason, reasonableness]
    2: the quality of being consistent with or based on logic [syn:
       rationality, rationalness]