Bertrand Russell and Ludwig Wittgenstein developed different, though closely related, versions of logical atomism. Wittgenstein's version is presented in Tractatus Logico-Philosophicus, and discussed in the various pre-Tractatus manuscripts. For Russell, analytical realism is a form of atomism because it maintains that the existence of the complex depends on the existence of the simple and not vice versa, and that the atomic entities in its ontology (universals and particulars) have their nature quite independently of the relations they bear to one another. The core tenets of Wittgenstein's logical atomism may be summarised as follows: Every proposition has a unique final analysis that reveals it to be a truth-function of elementary propositions; These elementary propositions assert the existence of atomic states of affairs; Elementary propositions are mutually independent — each one can be true or false independently of the truth or falsity of the others; Elementary propositions are immediate combinations of semantically simple symbols or ‘names’; Names refer to items wholly devoid of complexity, so-called ‘objects’; Atomic states of affairs are combinations of these simple objects.