Proof of an impossibility.
    It gives us a new idea of constructing.
   It clarifies our idea of constructing.
  An idea getting clearer.
  Impossibility of making coincide right & left hand.
  How does the ‘proof’ convince us of the
impossibility? As an experiment would? Can't he still look for a tr construction of the trisection? Certainly but the point of it has been removed for him.