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Ladder

Cardinality — the ladder

One essay so far against this idea. A ladder is the distinct arguments that stand against one idea, and this one has room to grow.
  1. [0, 1](0, 1)01½0 goes to a half and 1/n goes to 1/(n+2); every other point of [0, 1] stays where it is8 moved points drawn, all distinct, all inside (0, 1) — and the two endpoints are gone

    Two injections make a bijection

    If each of two collections fits inside the other without collisions, they are the same size. That sounds obvious and is not, because neither injection needs to be onto — and the proof is a rule for deciding which of the two to follow, one chain at a time.

    rung 1 · logic

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