Retortion

Retortion is the act of identifying a self-referential contradiction in an opponent's position.

So, for example, if I were to write, "No one can type a coherent sentence in English," a thoughtful critic might retort: "But what you just wrote provides evidence against what you claim to be true."

Retortion is spelled "retorsion" in French. The idea of turning an opponent's self-referential contradictions into a reason for rejecting the position is common among Transcendental Thomists, who used various forms of this argument to demonstrate the instability of Kant's epistemology.

Classical examples

St. Augustine, De Trinitate, 12-21; De Civitate Dei, XI, 26

Si fallor, sum.

Descartes

Cogito, ergo sum.

Strange certitudes

Heidegger, Intro to Metaphysics, 199

"No one can jump over his own shadow."

I know this is true. I know what a shadow is, I know what jumping is, and I see what he means. I don't know how to specify the premises that would turn this into a formal deduction, but I'm sure they could be spelled out eventually.

Links

• Moleski:
  • "Retortion: The Method and Metaphysics of Gaston Isaye."
  • "The Role of Retortion in the Cognitional Analyses of Lonergan and Polanyi."
  • Proving negatives.

• Wikipedia, "Self reference."
• Wikipedia, "Gödel's Incompleteness Theorems."