The heyday of emergentist thinking was in the 1920s, when it was seen as a middle position in the reductionist–vitalist debate. However, as a result of ambiguities in its original formulation and the rise on the larger philosophical scene of logical positivism, with its strong reductionist impulse, emergentism fell rapidly out of favor. However, since the 1970s it has undergone a revival, due on the one hand to the failure of reductionism to solve the problems of life and mind, and on the other to the invention of dynamical systems and complexity theories, which seem to cry out for an emergentist interpretation. Emergentism is by no means now orthodoxy, especially in the practice of science, where reductionism is still the default method, but in philosophy it is again taken quite seriously.

The situation for emergentism is if anything even better in the social sciences, where the issue (if not the term itself) was first taken up in the debate about methodological individualism in the 1950s. Although that debate was inconclusive, the importation of positivist philosophy of science in the 1960s and then the spread of rational choice theory from economics to the other social sciences gave the momentum to reductionism. Yet, in sociology macro-level theorizing never lost its premier position, and critical realists there like Roy Bhaskar and Margaret Archer were among the first to develop explicitly emergentist social theories; in economics it has become apparent that macro-theory cannot be reduced to micro; and in political science the rise of rational choice theory has been balanced by historical institutionalism, constructivism, and other non-reductionist social theories. So in the social sciences emergentism has always been a live option.

Emergentism and reductionism share at least one key assumption: a materialist ontology. This is not surprising for reductionism, which is all about showing how, not just macroscopic physical objects, but seemingly non-material phenomena such as life, consciousness, and social structures are all ultimately made of the material stuff ostensibly described by physics.