2 thoughts on “Symbol blog posts

  1. Hi John,

    Just a quick comment on the aside about ‘the exception proves the rule’ in your Math Symbols post. The word ‘prove’ in that phrase is a slightly archaic use of the word, meaning ‘to put to the test’, rather than the more common meaning of ‘to demonstrate as true’. The latter meaning makes no sense, of course.

    Exceptions (or apparent exceptions) put rules to the test because one must do some work to determine whether the exception is not really an exception because it’s specifically excluded by side conditions, or whether the rule itself needs refinement to account for the exception.

    I greatly enjoy reading your blog – keep up the good work.

  2. Actually, David, that’s a common but false interpretation. The “exception proves the rule” is a legal phrase coming from Latin long before the archaic English use of prove as test. The short summary is that the presence of an exception (a “No Parking” sign) proves that the opposite rule exists elsewhere (parking is normally allowed). See Snopes or Wikipedia for all the gory details. Wikipedia does reference the opposite interpretation but also points many other languages that have the expression, every one of which uses a word equivalent to confirm instead of test.

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