Please answer a question about the following article about Karl Popper:

According to John N. Gray, Popper held that "a theory is scientific only in so far as it is falsifiable, and should be given up as soon as it is falsified." By applying Popper's account of scientific method, Gray's Straw Dogs states that this would have "killed the theories of Darwin and Einstein at birth." When they were first advanced, Gray claims, each of them was "at odds with some available evidence; only later did evidence become available that gave them crucial support." Against this, Gray seeks to establish the irrationalist thesis that "the progress of science comes from acting against reason."

What kind of thesis does Gray advance about scientific progress?
irrationalist