Source : Webster's Revised Unabridged Dictionary (1913)

Externalism \Ex*ter"nal*ism\n.
   1. The quality of being manifest to the senses; external acts
      or appearances; regard for externals.

            This externalism gave Catholicism a great advantage
            on all sides.                         --E.
                                                  Eggleston.

   2. (Metaph.) That philosophy or doctrine which recognizes or
      deals only with externals, or objects of sense perception;
      positivism; phenomenalism.