Reductionism and antireductionism.

Reductionism is the idea that all of the complex and apparently disparate things we observe in the world can be explained in terms of universal principles governing their common ultimate constituents: that physics is the theory of everything. Antireductionism comes in two varieties: epistemological and ontological. Epistemological antireductionism holds that, given our finite mental capacities, we would not be able to grasp the ultimate physical explantation of many complex phenomena even if we knew the laws governing their ultimate constituents. Therefore we will always need special sciences like biology, which use more manageable descriptions. There may be controversy about which special sciences cannot be replaced by reduction, but that there will be some is uncontroversial. Ontological antireductionism holds, much more controversially, that certain higher-order phenomena cannot even in principle be fully explained by physics, but require additional principles that are not entailed by the laws governing the basic constituents. With respect to biology, the question is whether the existence and operation of highly complex functionally organized systems, and the appearance of self-replicating systems in the universe, can be accounted for in terms of particle physics alone, or whether they require independent principles of order.