Hard to Vary or Hardly Usable?
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With an account, you can revise, criticize, and comment on ideas.Deutsch’s stance in my own words:
The distinguishing characteristic between rationality and irrationality is that rationality is the search for good explanations. We make progress by searching for good explanations.
A good explanation is hard to vary “while still accounting for what it purports to account for.” (BoI chapter 1 glossary.) A bad explanation is easy to vary.
For example, the Persephone myth as an explanation of the seasons is easy to change without impacting its ability to explain the seasons. You could arbitrarily replace Persephone and other characters and the explanation would still ‘work’. The axis-tilt explanation of the earth, on the other hand, is hard to change without breaking it. You can’t just replace the axis with something else, say.
The quality of a theory is a matter of degrees. The harder it is to change a theory, the better that theory is. When deciding which explanation to adopt, we should “choose between [explanations] according to how good they are…: how hard to vary.” (BoI chatper 9; see similar remark in chapter 8.)
Deutsch leaves open how we find out how hard to vary an explanation is. We need more details. In some cases it’s obvious, but we need a general description for less-obvious cases.
Even if we allow creative user input, eg a score for the quality of an explanation, we run into all kinds of open questions, such as what upper and lower limits to use for the score, and unexpected behavior, such as criticisms pushing an explanation’s score beyond those limits.
Deutsch contradicts his yardstick for understanding a computational task. He says that you haven’t understood a computational task if you can’t program it. His method of decision-making based on finding good explanations is a computational task. He can’t program it, so he hasn’t understood it.
Isn’t this asking for a formalization of creativity, which is impossible?
No, it’s asking for a formalization of rational decision-making, which is a related but separate issue. Given a set of explanations (after they’ve already been created), what non-creative sorting algorithm do we use to find the best one?
Maybe Deutsch just means hard to vary as a heuristic, not as a full-fledged decision-making algorithm.
A heuristic or heuristic technique (problem solving, mental shortcut, rule of thumb) is any approach to problem solving that employs a pragmatic method that is not fully optimized, perfected, or rationalized, but is nevertheless "good enough" as an approximation or attribute substitution.
None of this means a heuristic couldn’t be programmed. On the contrary, heuristics sound easier to program than full-fledged, ‘proper’ algorithms.
I’d be happy to see some pseudo-code that uses workarounds/heuristics. That’d be a fine starting point.
@dirk-meulenbelt suggested in a space (at 21:30) that a bunch of epistemology is underspecified. There are many epistemological concepts (like criterion of democracy, falsifiability, etc.) that we don’t know enough about to express in code.
Yes, many ideas fail Deutsch’s yardstick. But so what? That doesn’t make things better.
Deutsch’s yardstick applies to computational tasks. It’s not meant for other things. It’s not clear to me that the criterion of democracy is a computational task.
Liberty said (at 1:38:39) hard to vary isn’t a method of decision-making. It’s a factor people take into account when they make decisions, but decision-making itself is a creative process.
I’m not saying hard to vary is a decision-making method. I’m saying it’s an integral part of Deutsch’s decision-making method. As I write in my article:
He argues that “we should choose between [explanations] according to how good they are…: how hard to vary.”
Liberty responded (1:39:46) that that quote is misleading because it makes it sound like hard to vary is the only criterion people use when making decisions, which can’t be true. There are other criteria, like “consistency with data”, “logical consistency”, “fitting in with existing theories”, etc.
The quote may be false, but I don’t see how it’s misleading. I’m not quoting Deutsch in isolation or cherry-picking information or anything like that.
Deutsch says to choose between explanations “according to how good they are” – note the plural.
What if I can only come up with one explanation? Can I just go with that one? What if it’s bad but still the best I could do? He leaves such questions open.
Deutsch says rationality means seeking good explanations, so without a step-by-step guide on how to seek good explanations, we cannot know when we are being irrational. That’s bad for error correction.
From my article:
[I]sn’t the difficulty of changing an explanation at least partly a property not of the explanation itself but of whoever is trying to change it? If I’m having difficulty changing it, maybe that’s because I lack imagination. Or maybe I’m just new to that field and an expert could easily change it. In which case the difficulty of changing an explanation is, again, not an objective property of that explanation but a subjective property of its critics. How could subjective properties be epistemologically fundamental?
fundamental
@zelalem-mekonnen suggested during a space (37:36) that hard to vary is just one mode of criticism.
Not according to Deutsch. He says hard to vary is epistemologically fundamental, that all progress is based on it. For example, he phrases testability in terms of hard to vary (BoI chapter 1):
When a formerly good explanation has been falsified by new observations, it is no longer a good explanation, because the problem has expanded to include those observations. Thus the standard scientific methodology of dropping theories when refuted by experiment is implied by the requirement for good explanations.
He also says that “good explanations [are] essential to science…” (thanks @tom-nassis for finding this quote). Recall that a good explanation is one that is hard to vary.
For Deutsch, hard to vary is the key mode of criticism, not just one of many.