I am trying to understand why this "proof" of Etm undecidability is wrong.
ALLtm={ < M >|M is a TM, L(M)=∑*}
ETM={< M >|M is a TM, L(M)=∅}
We know that ALLTM is undecidable, lets assume ETM is decidable (T is a TM that decides ETM) and get a contradiction.
S= "On input < M >, M is a TM:
1.Construct the following TM M1,
M1=" On input x:
1.Run M on x, if M accepts x, reject. otherwise, accept x."
2.Run T on input < M1 >.
3.If T accepts, accept, if T rejects, reject.
Why this reduction doesn't prove that Etm is undecidable?
(If w∈L(M) M1 rejects it, so if L(M)=∑*, L(M1)=∅.
If w∉L(M) (M doesn't stop on w or rejects) M1 accepts w, so if L(M)≠∑*, L(M1)≠∅).