Source : Webster's Revised Unabridged Dictionary (1913)

Illative \Il"la*tive\, a. [L. illativus: cf. F. illatif.]
   Relating to, dependent on, or denoting, illation;
   inferential; conclusive; as, an illative consequence or
   proposition; an illative word, as then, therefore, etc.

   {Illative conversion} (Logic), a converse or reverse
      statement of a proposition which in that form must be true
      because the original proposition is true.

   {Illative sense} (Metaph.), the faculty of the mind by which
      it apprehends the conditions and determines upon the
      correctness of inferences.