Reductionism

Reductionism refers to several related but different philosophical positions regarding the connections between phenomena, or theories, "reducing" one to another, usually considered "simpler" or more "basic".The Oxford Companion to Philosophy suggests that it is "one of the most used and abused terms in the philosophical lexicon" and suggests a three part division:

Reductionism can be applied to objects, phenomena, explanations, theories, and meanings.

In the sciences, application of methodological reductionism attempts explanation of entire systems in terms of their individual, constituent parts and their interactions. Thomas Nagel speaks of psychophysical reductionism (the attempted reduction of psychological phenomena to physics and chemistry), as do others and physico-chemical reductionism (the attempted reduction of biology to physics and chemistry), again as do others. In a very simplified and sometimes contested form, such reductionism is said to imply that a system is nothing but the sum of its parts. However, a more nuanced view is that a system is composed entirely of its parts, but the system will have features that none of the parts have. "The point of mechanistic explanations is usually showing how the higher level features arise from the parts."