reductionism

Short definition from Wiktionary

Noun

1. 1
   An approach to studying complex systems or ideas by reducing them to a set of simpler components.
2. 2
   A philosophical position which holds that a complex system is nothing but the sum of its parts, and that an account of it can be reduced to accounts of individual constituents. In a reductionist framework, the phenomena that can be explained completely in terms of relations between other more fundamental phenomena are called "epiphenomena".