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This week:
- Introducing mostly-truths
- Follow-ups to last week’s exercises
- Workbook: mostly-truths
The two chapters per week plan
Both are about truth: a central concern in both rationality and rationalism.
“Rationalism mistakenly supposes formal rationality’s theory of truth applies unambiguously in the real world” is one way of summarizing Part One of The Eggplant.
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“The value of meaninglessness”: A quick and easy read. A major breakthrough for rationalism was recognizing that statements may be neither true nor false, but meaningless. That was a first step toward a more sophisticated understanding of truth.
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“The truth of the matter”: A longer and more difficult chapter: two thousand words, or about six printed pages. Even in hard science, most truths are only mostly true. Formal rationality doesn’t work with “mostly truths.” Yet it does often work in science. What’s the resolution of this paradox?
Workbook follow-ups
Last week’s exercise prepared for this week’s. It suggested looking out for mostly-truths:
- When you encounter one, ask in what sense is this true? In what sense false?
- Is it a problem that this thing is not quite either true or false? Why or why not?
- What could you do about it, if it is a problem?
How did that go? What did you notice?
Also last week:
The feelings of meta-rationality include wonder, curiosity, amusement, playfulness, enjoyment, and creativity.
Can you remember concrete cases when any of those feelings arose during your technical work in the past week? Can you remember what triggered that?
(Something else to look out for!)
Workbook: working with mostly-truths
Read “The truth of the matter” before proceeding.
- What is the difference between “mostly true” and “usually but not always true”?
This distinction is critical because you can reason about “not always truths” probabilistically, but probability theory doesn’t work with “mostly truths.”
- Why not? (Do you remember? Did you get that bit?)
Near the end, “The truth of the matter” foreshadows a central point of Part Three of The Eggplant:
How do we reason formally without the absolute truths that formal reasoning methods formally require?
Some rational inferences turn out to be true enough under “reasonable” (non-rational) interpretation in a specific context. For this to work, we have to choose carefully which mostly-truths to work with. We have to know, or reason about, which formal inferences we can get away with—even though, starting from only-mostly truths, they are not logically sound.
Part Three explains how and when and why that works. We’ll need a complex conceptual background structure to understand the details—about 250 printed pages of theoretical explanation.
This week’s exercise suggests getting a direct, pre-theoretical understanding through observing your experience of doing rationality. I’m assuming here that you routinely and competently engage in some sort of systematic, rational work. If so, you do as a practice what Part Three describes in theory.
If you observe that practice accurately, you may not need the theory! You may figure out similar explanations for yourself. And Part Three will make much more sense when you get there.
- Look out for “mostly truths” in the course of your work.
- In situations where rationality mostly works, mostly-truths mostly don’t cause trouble. When you notice a mostly-truth, ask: why is it not a problem that this is not absolutely true?
- Pick one example that is usually only more-or-less true, rather than one that is usually absolutely true, but not always.
- Usually, you can’t list all the ways a mostly-truth might not be quite true. However, you can usually think of a few. For each way: concretely, why are you able to ignore that possibility?
- What specific factors in the situation make it feasible to treat the mostly-truth as though it is fully true?
- What are you doing to avoid or mitigate the possible problems not-altogether-truth might cause?
- What are other people in the situation doing to make the mostly-truth work out OK?
Noticing what you are doing and how and why, as you do rationality, is meta-rational reflection. Part Four, the heart of The Eggplant, is about that. This is a meta-rational exercise…
One approach to the logistics here is to make a mental note, “oh, this is a good example of a mostly-truth,” when you encounter one. Then spend half an hour in the evening going through the questions above. Perhaps write out brief answers in a notebook—paper or digital.
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