 It is also worth noting that Russell’s paradox was not the only paradox that troubled Russell and, hence, not the only motivation for the type restrictions one finds in Principia Mathematica. In his earlier work, The Principles of Mathematics, Russell devotes a chapter to “the Contradiction” (Russell’s paradox), presenting it in several forms and dismissing several non-starter responses. He then signals that he will “shortly” discuss the doctrine of types. This doesn’t happen for several hundred pages, until we reach the very end of the book, in Appendix B! There Russell presents an incipient, simple theory of types, not the theory of types we find in Principia Mathematica. Why was the later theory needed? The reason is that in Appendix B Russell also presents another paradox which he thinks cannot be resolved by means of the simple theory of types. This new paradox concerns propositions, not classes, and it, together with the semantic paradoxes, led Russell to formulate his ramified version of the theory of types. 