noun

• (uncountable, historical) The school of the sophists in antiquity; their beliefs and method of teaching philosophy and rhetoric.
  "Within the framework of democracy a new ideology, born of sophism, took root and proclaimed the rights of the individual in all spheres, political as well as moral."
• (countable) A flawed argument, superficially correct in its reasoning, usually designed to deceive.
  "The hope of improvement is a quality at once so strong and so excellent in the human mind, that I, for one, disapprove of any sophism—or, if you will, argument—that tends to repress it."
• (countable) An intentional fallacy.
• (uncountable) Sophistic, fallacious reasoning or argumentation.
  "What! No demonstration of the Being of God! No abstract arguments! No proofs a priori! Are these, which have hitherto been so much insisted on by philosophers, all fallacy, all sophism? Can we reach no further in this subject than experience and probability?"