4.2 Irrational Method

When demonstrating the same thing, there is also this method of doing it.
When p implies q needs to be demonstrated, we still assume the condition
with assume p in the proof. Then we will deny the conclusion by stating
assume not q.

p implies q

proof

assume p;

assume not q;

······

thus contradiction;

end:

And then we will lead from this and state thus contradiction. It means that a

irrational method was used. If we assume that it is neither p nor q, it means

that an inconsistency occurred.