Is this a valid variation on modus tollens? If not P,

>>2747220
Let's try this out then:
>If it doesn't breathe then it's dead
>It's not dead
>Therefore, it breathes
Now tell me if you think that's correct

>>2747253
that's a bad example

>>2747275
It's a perfectly valid example.

>>2747289
It sounds true this way. But i need something stronger, like a formal proof.

>>2747253
OP's question is about validity though. In your example, the structure is valid, but the first premise is false.

>>2747253
You are retarded, its more like
>if its not blue its yellow
>not yellow
>therefore unspecified

>>2747289
it's perfectly valid, and if the first premise were true, then the conclusion would be true.

Yes, it's fine, by negation of negation. You just skipped a step.

if not p then q
not q
therefore not not p MT
not not p
p NN

>>2747322
There's a difference between validity and soundness.

>>2747386
I know, and OP's question was about validity.

>>2747275
I think this is a clearer example

If you're not unemployed, then you have a job.
You don't have a job
Therefore you're unemployed