My goal was not to defend pure empiricism - that justifications for knowledge can come only from sense data. I just wanted to emphasize that, in your example, when we chose a good explanation instead of a bad one, the goodness of the explanation has a large empirical component.I am guessing that you agree with this but would focus on the non-empirical component. One non-empirical component of its goodness would be the complexity of its specification, the Kolmogorov complexity for instance.