This article addresses the issue of objectivism vs constructivism in two areas,biology and cognitive science, which areintermediate between the natural sciences suchas physics (where objectivism is dominant) andthe human and social sciences (whereconstructivism is widespread). The issues inbiology and in cognitive science are intimatelyrelated; in each of these twin areas, the objectivism vs constructivism issue isinterestingly and rather evenly balanced; as aresult, this issue engenders two contrastingparadigms, each of which has substantialspecific scientific content. The neo-Darwinianparadigm in biology is closely resonant withthe classical cognitivist paradigm in cognitivescience, and both of them are intrinsicallyobjectivist. The organismic paradigm inbiology, based on the concept of autopoiesis,is consonant with the paradigm of enaction incognitive science; the latter paradigms are bothprofoundly constructivist.In cognitive science, the objectivism vsconstructivism issue is internal to thescientific field itself and reflexivity isinescapable. At this level, strong ontologicalobjectivism is self-contradictory and thereforeuntenable. Radical constructivism isself-coherent; but it also rehabilitatesa weak form of objectivism as a pragmaticallyviable alternative. In conclusion, there is aneven-handed reciprocity between objectivistand constructivist perspectives. Finally, thearticle examines the consequences of thisconclusion for fields other than cognitivescience: biology; physics and the naturalsciences; and the human and social sciences.