How is John Proctor the tragic hero?

John Proctor is a paradox. He is fiercely honest yet he cheats on his wife Elizabeth. It is this conflict in his personality that eats away at him and eventually caused his demise. Unlike Mr. Putnam or Reverend Parris, Proctor cannot reconcile himself to lies and deceit. He tears himself apart trying to live up to his untarnished name yet endure the frailties of his nature.