WordNet (r) 3.0 (2006):

positivistic
    adj 1: of or relating to positivism; "positivist thinkers";
           "positivist doctrine"; "positive philosophy" [syn:
           positivist, positivistic, positive]

Moby Thesaurus II by Grady Ward, 1.0:

90 Moby Thesaurus words for "positivistic":
   Cyrenaic, Eleatic, Epicurean, Marxian, Marxist, Megarian, Stoic,
   animist, animistic, atomistic, bigoted, commonsense, conceited,
   cosmotheistic, doctrinaire, doctrinarian, dogmatic, dogmatizing,
   down-to-earth, earthy, eclectic, empirical, eudaemonistic,
   existential, hardheaded, hedonic, hedonist, hedonistic, humanist,
   humanistic, hylomorphous, hylotheistic, idealistic,
   instrumentalist, materialist, materialistic, matter-of-fact,
   mechanist, mechanistic, metaphysical, monistic, naturalist,
   naturalistic, nominalist, opinionated, opinionative, opinioned,
   oracular, panlogistical, pantheistic, peremptory, pontifical,
   positive, positivist, practical, practical-minded, pragmatic,
   pragmatist, pronunciative, rational, rationalistic, realist,
   realistic, reasonable, sane, scholastic, scientific, scientistic,
   secular, self-opinionated, self-opinioned, sensationalistic,
   sensible, sober-minded, sound, sound-thinking, straight-thinking,
   syncretistic, theistic, transcendentalist, transcendentalistic,
   unideal, unidealistic, unromantic, unsentimental, utilitarian,
   vitalistic, voluntarist, voluntaristic, worldly