Chisholm then continues by imagining a series of worlds in which Adam and Noah gradually swap letters in their names. This series ends with a world in which they have “swapped names” altogether. In that world, Adam is called ‘Noah’, and Noah is called ‘Adam’.[5] Going still further, Chisholm imagines a world, wn, in which Adam and Noah have swapped all their qualitative properties, so that in wn Adam has all the properties that Noah has in w1, and Noah has all the properties that Adam has in w1. Then Chisholm asks a series of tough questions: