First of, I think it is too early to claim this:
We will have to wait for Steinhardt and co’s response to see if they agree with this analysis.
I personally find fine tuning arguments to be ill-posed. However, if one believes in the fine-tuning problem, there is an interesting give and take with inflation here:
- There are other fine-tuning problems in physics. Indeed, the fine-tuning problem of inflation is a relatively recent addition to the list of fine-tuning problems in physics. An example is the supposedly fine-tuned ratio of the strengths of the electromagnetic and gravitational interactions.
- The most popular way to explain away these fine-tuned parameters is to assume a multiverse initiated by inflation. By the anthropic principle, we must then live in a universe that looks as if it is fine tuned. See here for more explanation.
- However, as Martin’s paper points out, the inflationary multiverse is a speculation.
- If the multiverse speculation is correct, then inflation has a problem (at least according to Steinhardt and co), as this means that inflation loses predictive power and there is no empirical way to test inflationary theories.
- If the multiverse speculation is false, then we lose our explanation for the other non-inflation fine-tuned parameters.
To reiterate, which would one want to sacrifice: the predictive power (and thus the empirical and epistemological status) of inflationary theories, or the lack of fine-tuning of various physical parameters?
Again, to me this discussion is somewhat moot (or at least premature), as I think that fine-tuning arguments (be it inflationary or not) is ill-posed.