Gottlob: Write Code in Frege's Concept Notation

In 1879, Gottlob Frege wrote the Begriffsschrift, an attempt at a logically perfect language. Begriffsschrift is often translated to "concept-script," essentially a formula language, an arithmetic for pure thought. It was intended as a "system of evaluation that will make it a mechanical task, once an inference is expressed, to determine whether or not it is correct and gapless," as Joan Weiner puts it in Frege Explained

This new system clarified and dispelled ambiguities of language that had seeped into logical analysis, making it easier to differentiate logical relationships apart from the content of the specific claim being investigated, more or less founding the movement of analytical philosophy. However, where Frege's legacy was huge, his notation system was never widely adopted. Frege saw it as simple, but others found the bars and the mix of German and Greek characters overly ornate. Only a few disassociated symbols from Frege's system are still in use, such as the turnstile ⊢ operator in symbolic logic, meaning "provable." But there it has been stripped of its context: in Frege's system, it sits at the upper left of all his diagrams (see the two images above), serving as an entry point to an assertion and the propositions used to evaluate it. So granular was Frege's design, he ascribed meaning to both its marks. A horizontal line alone refers to a combination of ideas, it's the vertical mark that indicates that the resulting combination can hold a truth value.

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This entry originally appeared at esoteric.codes/blog/gottlob-write-code-in-freges-concept-notation, and may be a summary or abridged version.