# Mathematical rules of reasonable expectation

#### Mathematical rules of reasonable expectation

- Event time: 11:30am
- Event date: 3rd December 2014
- Speaker: Professor Richard Blythe (School of Physics & Astronomy, University of Edinburgh)
- Location: Room 2511, James Clerk Maxwell Building (JCMB) James Clerk Maxwell Building Peter Guthrie Tait Road Edinburgh EH9 3FD GB

### Event details

Proposition A: The Condensed Matter group Christmas dinner is on Tuesday evening.

Proposition B: Turnout at this week's Theory Club is low.

If A implies B, Aristotle would tell us that the only logical deduction we can make is that a high attendance on Wednesday would imply that there had been no Christmas dinner the night before. On the other hand, if no-one shows up, that doesn’t necessarily mean that there had been a festive knees-up the night before, but it makes this proposition more plausible.

It turns out that one can assign a number to each proposition that serves as a measure of its plausibility, and that by putting very light constraints on how these plausibilities should relate to each other, obtain a set of algebraic rules that they must satisfy. These rules coincide with those of probability theory, but at no point do we need to make reference to ensemble an theory clubs and Christmas dinners. I shall attempt to explain why and what I would like this to mean.

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