4 ms·
The thing which is not. In most mathematical logic systems "false" or "⊥" has the nice property that anything can be derived from it (⊥ -> p, for any sentence
by H8crilA 7y ago
The thing which is not.
In most mathematical logic systems "false" or "⊥" has the nice property that anything can be derived from it (⊥ -> p, for any sentence p). I find it funny that the undefined behavior of null dereferencing works the same way in C - literally anything can happen to the program, so the compiler is free to assume (derive about the current state of execution) anything it wants.
- silasdavis 7y agoAnything can be derived from p or not p, not from false.
- thegeomaster 7y agoThis is just a corollary of the fact that "p or not p" is false (for any value of p).
- pretty_lorelei 7y ago"p and not p" is false, "p or not p" is always true.
- thegeomaster 7y agoOops. Went a bit on autopilot with that one.
- rq1 7y agoThen everything is true. :)
- H8crilA 7y agoThe sentence "p or not p" is a tautology ("true", ⊤) in classical logic, so you can't derive anything useful from it. It can carry some power in non-classical logics, like the intuitionistic logic, where it's not true that "p or not p" for any sentence p. You can derive anything from false, this is known as the principle of explosion: "ex falso quodlibet", "from false anything": https://en.wikipedia.org/wiki/Principle_of_explosion https://en.wikipedia.org/wiki/Principle_of_explosion
- dooglius 7y agoIt's not so much "funny" as a rather obvious consequence of the principal