# How Does the Brain Do Plausible Reasoning?

## Abstract

We start from the observation that the human brain does plausible reasoning in a fairly definite way. It is shown that there is only a single set of rules for doing this which is consistent and in qualitative correspondence with common sense. These rules are simply the equations of probability theory, and they can be deduced without any reference to frequencies.

We conclude that the method of maximum—entropy inference and the use of Bayes’ theorem are statistical techniques fully as valid as any based on the frequency interpretation of probability. Their introduction enables us to broaden the scope of statistical inference so that it includes both communication theory and thermodynamics as special cases.

The program of statistical inference is thus formulated in a new way. We regard the general problem of statistical inference as that of devising new consistent principles by which we can translate “raw” information into numerical values of probabilities, so that the Laplace—Bayes model is enabled to operate on more and more different kinds of information. That there must exist many such principles, as yet undiscovered, is shown by the simple fact that our brains do this every day.

## Keywords

Common Sense Communication Theory Plausible Reasoning Probability Assignment Frequency Theory## Preview

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## References

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