Jane: Professor Harper' s ideas for modifying the design of guitars are of no value because there is no general agreement among musicians as to what a guitar should sound like and, consequently, no widely accepted basis for evaluating the merits of a guitar' s sound  Mark: What' s more, Harper' s ideas have had enough time to be adopted if they really resulted in superior sound
It took only ten years for the Torres design for guitars to be almost universally adopted because of the improvement it makes in tonal quality
Mark and Jane use similar techniques to argue for different conclusions.