 W4 entails both W2 and W3, and in turn each of them entails W1. All the same, W\(4'\) entails both W\(2'\) and W\(3'\), and in turn each of them entails W\(1'\). No Twins is a consequence of W1. Under the assumption that No Twins is true, each W\(i\) is equivalent to W\(i'\). So each W\(i\) entails W\(i'\). W\(4'\) entails all the Bs. W\(1'\) entails Plenitude. W4 is thus an extremely strong principle, since it entails all the principles we have met so far. See Figure 2.