20. Infer.

21. Might.

22. The tradition was that there had once been a huge island to the west of Europe, beyond which lay another continent. The island, called Atlantis, was said to have been swallowed up by an earthquake, leaving behind a great ocean, the Atlantic, separating Europe from the unknown continent. There is an account of the inhabitants and laws of the lost Atlantis in the Critias, or Atlanticus as it was subtitled in early editions of Plato.

23. Entirely.