"Inflation does not provide a natural explanation for why the early universe looks like it does unless you can give me an answer for why inflation ever started in the first place. That is not a question we know the answer to right now. That is why we need to go back before inflation into before the Big Bang, into a different part of the universe to understand why inflation happened versus something else. There you get into branes and the cyclic universe. ... I really don't like any of the models that are on the market right now. We really need to think harder about what the universe should look like."