David Deutsch’s idea of hard to vary is also a degree approach: look at the degree/amount of hardness to vary.
I think there’s a way of recasting hard-to-vary as a decisive approach, which is basically the answer ET gave to my first question in this thread.
edit: To be clearer about what I mean, the connection is that if a theory is easy to vary, that means by definition that it contains some unnecessary baggage. On those grounds it can be criticized decisively as not meeting certain (good) goals, such as the goal of having theories without unnecessary baggage.
We should always act on a non-refuted IGC. Why? Better something without a known error than with a known error. That’s what using our knowledge instead of ignoring it means.
I noticed how different this is from the conventional view of errors.
In the conventional view, known errors are completely unavoidable. For example, speaking from the conventional viewpoint: I think of my floor as a rectangle, and that theory has some errors because my floor is not a perfect rectangle. On this view, it wouldn’t make sense to always prefer things without known errors, because if that was your preference then you could never do anything in the real world.
In the CF view, known errors are avoidable. The idea that my floor is a rectangle can only be judged as having an error if it is part of an IGC triplet, and if the goal is something like “I want to put my rectangular desk flush against the wall,” then I know of no errors in that IGC triplet.
Earlier in the essay there is some stuff about variations on ideas:
The reason ideas can’t change from refuted to non-refuted is that if you change an idea to fix some problem, now you have a different idea. That’s a variant idea, not the same idea. The original idea without the fix is still refuted, and the new version was never refuted at any time because the criticism of the original idea does not apply to the new variant. People sometimes refer to many versions of an idea by the same name, e.g. “democracy” or “induction”. We can get away with this sometimes but it also leads to a lot of confusion. In some conversations, it helps to give each variant of an idea a different name. You can use descriptive names (“direct democracy”) or numbers (“induction-7”). We could specify dozens of different versions of direct democracy, and number them, but we usually don’t; we try to allocate precision where it’s actually useful, and most conversations don’t rely on precise nuances about democracy.
Later in the essay there is a comment about Objectivism:
If you do creative research, and come up with new knowledge, you’re actually changing the context! Creating new background knowledge doesn’t actually refute the old IGCs. What it can refute is the old I and G combined with the new C, which is useful. (This is related to Objectivism’s idea of contextual knowledge, which says ideas can remain non-refuted in a prior context even as you learn new things that refute them. Objectivism likes to view progress in terms of moving on to new, better knowledge without invalidating our old knowledge – it still had value and was useful in its context even if we know better today. That contrasts with the Critical Rationalism’s view of progress as a succession of new problems and errors, and belief that all our ideas are flawed/imperfect. Despite the different emphasis, these views are actually basically compatible. Progress involves getting closer to perfection without reaching it, and you can look at that in terms of making improvements, correcting errors, or both.)
The context in which a new variant of a refuted idea can still be used is set by its successor. That variant incorporates knowledge about the circumstances in which the old idea doesn’t work for some problem.