I just remembered a conversation I had (in german) about 18 years ago and the other person used the (german) term "All Theorie", which in this context was not related to the theory of everything but instead it is about the fact, that a proof can be shown not to be a valid proof, if it can prove any other hypothesis just as well (e.g. the opposite hypothesis or something entirely unrelated). I was not sure what the definition and the English term for this logical mistake is, nor can I remember a canonical example.
I tried to google the term but it seems my search always leads to the TOE instead of what I am looking for.
Can anyone here help me out?
EDIT Maybe I should give a (hopefully not all too flawed) example of what I mean. In the dark ages, the inquisition believed to "proof" witchcraft of a person by means of torture. But they could have "proven" any other theory with the same flawed method. For example, they could have made them confess they are actually pink, flying bunnies in disguise. And because that is so, the "proof" is flawed.