Theory Change and Degrees of Success

Scientific realism is the position that success of a scientific theory licenses an inference to its approximate truth. The argument from pessimistic metainduction maintains that this inference is undermined due to the existence of theories from the history of science that were successful but false. I aim to counter pessimistic metainduction and defend scientific realism. To do this, I adopt a notion of success that admits of degrees and show that our current best theories enjoy far higher degrees of success than any of the successful but refuted theories of the past.