 In the next subsections, we describe the two ways of deriving a contradiction from Basic Law V that Frege described in the Appendix to Gg. The first establishes the contradiction directly, without any special definitions. The second deploys the membership relation and more closely follows Russell’s Paradox. As we shall see, the following combination is a volatile mix: (a) the Comprehension Principle for concepts, which ensures that there is a concept corresponding to every formula with free variable \(x\), (b) the Existence of Extensions principle, which ensures every concept is correlated with an extension, and (c) Basic Law V, which ensures that the correlation of concepts with extensions behaves in a certain way.