Logical Atomism is a philosophical belief that originated in the early 20th century with the development of Analytic philosophy. Its principal exponents were the British philosopher Bertrand Russell, the early work of his Austrian-born colleague Ludwig Wittgenstein, and his German counterpart Rudolf Carnap.
The theory proposes that language, like other components of the world, consists of ultimate logical "parts" (or "atoms") that cannot be broken down any further. In order to understand ordinary language, we must perform "analysis" upon it, attempting to break it down to these elemental components. Russell and Wittgenstein disagreed as to the nature of these elementary components, and in his Philosophical Investigations, Wittgenstein rejected them.
The name for this kind of theory was coined in 1918 by Russell in response to what he called "Logical holism"; i.e. the belief that the world operates in such a way that no part can be known without the whole being known first. This belief is commonly called Monism, and in particular, Russell (and G.E. Moore) reacted to Absolute idealism dominant then in Britain.