The main goal in this book is to attempt a global account of Russell’s views on relations, by considering them as the very kernel of the fundamental problems and difficulties he faced in trying to build up a consistent, scientific philosophy. It will maintained that: (i) the ontology of relations (as implied in the problem whether relations can or cannot be regarded as terms), and related notions (such as order, form, structure, and, in general, complexes) underlay Russell’s main problems at each stage of his whole philosophical development; (ii) Bradley’s paradox of relations (which can also affect Wittgenstein’s “formal concepts”, i.e. class, function, predicate, proposition, and of course form and structure), is very useful, together with Frege’s paradox of concepts and Moore's paradox of truth, as a touchstone to discuss Russell’s several attempts to find a way out to those problems.