Mechanisms for reproductive isolation. With these auxilliary hypotheses, all sorts of testable predictions can be made, predictions which can be verified or falsified. As Walter pointed out, some predictions of earlier versions of evolution WERE falsified. Gene duplications was added as a source of variation. The evolutionary importance of small, isolated sub-populations was reassessed.
Hypotheses can slip from one category to the other.
It makes testable predictions and can be falsified. Walter argues that the flexibility offered by the auxilliary hypotheses is a bad thing. That is not a test. If we do not observe the experimental result expected by ether, then ether-ologists can always claim we haven't tried hard enough or long enough. They offer a situation that might help confirm ether theory as true.