Holism (from holos, a Greek word meaning all, whole, entire, total) is the idea that natural systems (physical, biological, chemical, social, economic, mental, linguistic, etc.) and their properties should be viewed as wholes, not as collections of parts. This often includes the view that systems function as wholes and that their functioning cannot be fully understood solely in terms of their component parts.

Reductionism is often viewed as the opposite of holism. Reductionism in science says that a complex system can be explained by reduction to its fundamental parts. For example, the processes of biology are reducible to chemistry and the laws of chemistry are explained by physics.

Social scientist and physician Nicholas A. Christakis explains that "for the last few centuries, the Cartesian project in science has been attempting to break matter down into ever smaller bits, in the pursuit of understanding. And this works, to some extent... but putting things back together in order to understand them is harder, and typically comes later in the development of a scientist or in the development of science."

http://en.wikipedia.org/wiki/Holism