[Biomedical research: the debate on the reduction and emergence concepts].

The theoretical bases of medical knowledge exert a strong influence on both clinical practice and representations of living and health. In this perspective, reduction and emergence notions play a major role. Microreduction is the predominant analytical strategy used today in biology, as it is usually considered that essential life mechanisms can be reduced to molecular processes. Likewise, macroreduction proposes that parts can be defined in terms of their belonging to wholes, as it is usually assumed, for instance, in genetic epidemiology. With regard to emergence, this notion, which focuses on properties of a whole that cannot be deduced from properties of its parts, is consistent with both nature of living and evolution theory. The apparent success of reduction like analytical modality has generated in scientific community and public opinion an ideological reductionism, which corresponds, ontologically, to both physicalism (things can be entirely understood in terms of their parts), and atomism (things go their own way, independently of other things). Genetic reductionism has generated new cosmological representations of living, where past, present and future of living beings could potentially be deduced from fallacious, simple views of genome sequences. These views may lead to quantitative or qualitative definitions of standard patterns and hierarchies. In practical terms, research activity should integrate limits, strains as well as reductionism advantages. Biologists should also consider risks associated with an ideological, unrestricted reductionism, applied to any existence aspect, a notion with questionable legitimacy and with potential ethical, philosophical, and political involvements that go beyond the simple selection of a research strategy.