Monday, August 03, 2009

Some Implications & Presuppositions of MarshalPlan (Multiplicity and Simplicity Are Not Cause for Embarrassment or Regret)

During the last several months I have been posting updates of MarshalPlan. Now it is time to say a few words about the implications of MarshalPlan for epistemology and inferential theory. I have written before in a theoretical vein about MarshalPlan. See Tillers & Schum, "A Theory of Preliminary Fact Investigation" (1991). Now I just want to make some brief observations about two striking features of MarshalPan: (1) the multiplicity of evidence marshaling strategies in MarshalPlan and (ii) the simplicity of many of the evidence marshaling strategies found in MarshalPlan.

If some one were to ask me, "What is the key to factual inference?," I might give a variety of answers. My first response might be to say that there is no key to factual inference. I would say that drawing inferences requires the use of many keys.

If someone were to say to me that one logic (e.g., Bayesian logic) animates or underlies all valid factual inference, I should say, "Even if that is true -- even granting your premise -- it does not follow that only that one logic is needed to do inference. It is as if you said to me, 'A trip to Mars requires the equation F = MA.' In response, I would say, 'Yes, perhaps you're right, but making a trip to Mars requires a great many other things as well. In any event, although some of the things I must do to get to Mars -- e.g., get astronauts to read dials carefully or get machines to record sensory signals to a certain degree of accuracy -- may well be governed by F = MA (or by some other universal equation or equations of your choice), I don't yet understand precisely how reading dials is governed by that equation and, until [and unless] I do, I will have to use something other than F = MA to teach astronauts (or machines) how to read dials carefully and accurately.' So, you see, in addition to a rule such as Bayes' Theorem, I need procedures for storing legal rules, making legal arguments, constructing time lines, keeping track of persons, thinking about possibilities, and so on, and on, and on."

Common sense is, yes, well, aw shucks, quite common. But that does not mean common sense lacks intelligence. If common sense and intuitive sense were not "intelligent," man would long since have perished from the earth. (I grant you that this argument suggests that sharks are quite intelligent. Yes, in certain respects, they are quite intelligent. That is one reason why they have existed -- apparently -- for hundreds of millions of years.)

I think that in many respects the miracle of the human mind is like the miracle of human life: we do not understand very well how we manage to think as well as we do but in fact our seemingly shoddy and shabby and sloppy methods of thinking often work quite well, thank you. So if the "formal evidence marshaling strategies" found in MarshalPlan look and are relatively simple, that does not necessarily count against them: they may be simple devices for evoking simple but intelligent, or effective, ways of thinking. Yes, I grant you, it almost surely must be the case that very complex processes produce, or underlie, these simple forms of conscious thinking and ordering, and it may also be the case that if we could grasp and explicitly describe those complex processes, we could think and infer much better than we do at present. But we cannot wait until heaven arrives. We must make our best guesses now.

I have often puzzled over fuzzy logic. Despite occasional claims to the contrary, I have the sense that fuzzy logic is sometimes a powerful tool for the management (control) of real-world processes. That this should be so may seem a mystery -- because fuzzy logic, to the extent that I understand it, is far more akin to a semantic theory than to a causal theory; that is, although fuzzy logic largely or entirely abjures causal accounts of natural processes, it often seems to control those selfsame natural processes quite nicely, thank you. How is this possible?

My guess is that the power of fuzzy logic in the world of nature is possible because (i) fuzzy logic is indeed at heart a semantic theory and (ii) our words and concepts (including our ordinary words and concepts) somehow harbor, in a way we do not understand, much knowledge about our world.

I think some analogous notion may explain why the "ordinary" and "commonsense" procedures found in MarhalPlan work -- and why they work as well as they do (if, that is, they do work well).

Carefully disassembling -- and reassembling -- our common ways of knowing the world and making guesses about it may lead to important advances in our understanding of our ways of understanding the world. If I can achieve on a legal plane just a small fraction of the things that Lotfi Zadeh has accomplished in fields such as logic and common sense reasoning in general, I would die a happy man (to the extent, at least, that intellectual endeavors and accomplishments account for happiness).


The dynamic evidence page

Coming soon: the law of evidence on Spindle Law

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