 In Twins E2 can give s justification for believing P2 only if s has independent justification for believing Q2 in the first instance. Suppose that s does have independent justification for believing Q2, and imagine that s learns E2. In this case s will acquire justification for believing P2 from E2. But it is intuitive that s will acquire no justification for Q2 in virtue of her justification for believing P2 based on E2 and her knowledge of the inferential link between P2 and Q2. So Twins instantiates transmission failure when Q2 is independently justified.