 One significant and remaining challenge in the philosophy of macroevolution is to work out how the various ideas about macroevolution surveyed above may or may not fit together. What exactly is the relationship between punctuated equilibria and species selection? Or between PE and the major transitions? Or between species selection and historical contingency? Or between contingency and the major transitions? Do (some, all of) these ideas weave together to form a unified picture of evolution at large scales? Or do they represent something more like a heterogeneous grab bag of scientific ideas that are more or less useful in different contexts? A further question is how the relative (dis)unity of macroevolutionary theory might bear on the longstanding question of how macroevolution is related to microevolution.