The Collaborative International Dictionary of English v.0.48:

Moderatism \Mod"er*a*tism\ (m[o^]d"[~e]r*[asl]*t[i^]z'm), n.
   Moderation in doctrines or opinion, especially in politics or
   religion.
   [1913 Webster]

WordNet (r) 3.0 (2006):

moderatism
    n 1: a political philosophy of avoiding the extremes of left and
         right by taking a moderate position or course of action
         [syn: centrism, moderatism]