Stage performances are judged to be realistic to the degree that actors reproduce on stage the behaviors generally associated by audiences with the emotional states of the characters portrayed.
Conclusion (therefore)
Audiences will judge the performances of Method actors to be more realistic than the performances of traditional actors.
Evidence
Audiences judge realism based on the degree to which actors reproduce the behaviors an audience would associate with the emotional states of the characters portrayed.
Traditional actors imitate those behaviors. Method actors experience the same emotional states as their characters.
Evaluate
We know that the metric for judging realism is how well the actor .
If the author thinks that audiences will find Method actors more realistic, then he assumes that Method actors .
All we know about Traditional vs. Method is "imitating those behaviors" vs. "experiencing that emotional state".
Goal
So the argument assumes that someone who is "experiencing an emotional state" will do a better job reproducing the behaviors generally associated with that emotional state than will someone who is merely imitating those behaviors.