A philosophical doctrine may either facilitate or hinder the exploration of reality. For example, realism favors such exploration, whereas constructivism-relativism is hostile to it. And a philosophy may be ambivalent: enlightened in some respects and obscurantist in others. For instance, Descartes' mind-body dualism was a bane for psychology and psychiatry because it encouraged brainless speculation , but a boon to biomedical research because it justified dissection and vivisection. Rousseau was progressive in political philosophy but reactionary with regard to science. Romanticism was revolutionary in art but reactionary in philosophy. Positivism exalted scientific research while hindering it for attempting to restrict it to describing appearances. And Marxism benefited the social sciences in stressing the centrality of the so-called material factors, but harmed it in underestimating other factors and in adopting Hegel's obscurities and confusions.