Knaph
Explore

Proof by contradiction

Showing a claim is false by pretending it is true and following it to something impossible (reductio ad absurdum). If it leads to the impossible, its opposite must be true.

Depth 1 · Foundation

You can follow and build a proof by contradiction: suppose the claim, reach something impossible, conclude the opposite.

Sign in to prove what you know with a short quiz, see how deep you've gone, and earn XP for it.

Sign in with Google

Depths of understanding

  1. 1

    Foundation

    You can follow and build a proof by contradiction: suppose the claim, reach something impossible, conclude the opposite.

    Opens after

    ValidityProof by contradiction is a valid move: what leads to the impossible can't be true.NegationIt ends by accepting the opposite of the claim it started from.

Your path here

What's still between you and Proof by contradiction, depth 1, in the order you can learn it.

  1. 1ClaimDepth 1 · Foundation · Logic
  2. 2ArgumentDepth 1 · Foundation · Logic
  3. 3ValidityDepth 1 · Foundation · Logic
  4. 4All, some and noneDepth 1 · Foundation · Logic
  5. 5NegationDepth 1 · Foundation · Logic
  6. 6Proof by contradictionDepth 1 · Foundation · Logic

Builds on

Opens up

Nothing yet.