Popper on choosing between theories

I, by contrast, propose that the first thing to be taken into account should be the severity of tests… And I hold that what ultimately decides the fate of a theory is the result of a test, i.e. an agreement about basic statements… for me the choice is decisively influenced by the application of the theory and the acceptance of the basic statements in connection with this application…

This is in opposition to preferring the simple on an aesthetic basis. More importantly, he suggests we agree on the basic statements, and not universals.

He draws a long analogy to trial by jury:

The verdict is reached in accordance with a procedure which is governed by rules. These rules are based on certain fundamental principles which are chiefly, if not solely, designed to result in the discovery of objective truth. They sometimes leave room not only for subjective convictions but even for subjective bias.

The ideal these days, I guess, is that everyone can play juror if data are made available. Of course, taking data as basic (or near-basic) statements requires a decision.

The empirical basis of objective science has thus nothing ‘absolute’ about it. Science does not rest upon solid bedrock. The bold structure of its theories rises, as it were, above a swamp.

I see no reason not to believe this. The question is, then, to what extent can the theories built upon the swamp be objective — in particular, when most measurements have an associated error? We need to get into Popper’s treatment of probability before we can deal with this question.