if a, then B
A
therefore B
Modus Ponens.. A man-made rule of inference. If the two above premises are true, the conclusion (my skin will burn) must be true. It's a logical consequent. And it works in reality. Logic also demands consistency.
Logic doesn't deal with truth or falsity. It deals with validity. An argument can be valid, but still have false premises:
If I kick a duck, then it will cry like a little girl
I kick a duck
Therefore, it will cry like a little girl.
This is a perfectly valid argument, because the premises, if true, lead to the conclusion. It is of course not true, If I kick a duck, odds are I'd be using my health insurance card
It is a tool, but it works on principles about reality that we have discovered. Sorry, I'm tired, and I'm not doing the explanation justice.