He's leaning on the fact that theories are only provisionally true. No matter how mathematically certain we are, there is always a (perhaps infinitely tiny) chance that we are wrong. And there's his out.
"There is evidence for evolution, gobs and gobs of it. It is not just speculation or a faith choice or an assumption or a religion. It is a productive framework for lots of biological research, and it has amazing explanatory power. There is no conspiracy to hide the truth about the failure of evolution. There has really been no failure of evolution as a scientific theory. It works, and it works well...There is evidence for evolution, and evolution is an extremely successful scientific theory. That doesn't make it ultimately true, and it doesn't mean that there could not possibly be viable alternatives."
Dr. Todd Wood