theory, developed primarily by the British logician Bertrand Russell (Russell, Bertrand) and the Austrian-born philosopher Ludwig Wittgenstein, proposing that language, like other phenomena, can be analyzed in terms of aggregates of fixed, irreducible units or elements. Logical Atomism supposes that a perfect one-to-one correspondence exists between an “atom” of language (an atomic proposition) and an atomic fact; thus, for each atomic fact there is a corresponding atomic proposition. An atomic proposition is one that asserts that a certain thing has a certain quality (e.g.: “This is red.”). An atomic fact is the simplest kind of fact and consists in the possession of a quality by some specific, individual thing. Therefore, on the assumption that language mirrors reality, it can be proposed that the world is composed of facts that are utterly simple and comprehensible.

Through mathematical logic laid down in Principia Mathematica (1910–13; with Alfred North Whitehead), Russell sought to show that philosophical arguments could be solved in much the same way mathematical problems are solved. He rejected Hegel's monism, maintaining that it led to a denial of relations between things. For Russell, atomic propositions are the building blocks from which, using logical connectives, the more complex molecular propositions are constructed.