A note on proofs of existence of Nash equilibria in finite strategic games, of two players

Known general proofs of Nash's Theorem (about the existence of Nash Equilibria (NEa) in finite strategic games) rely on the use of a fixed point theorem (e.g. Brouwer's or Kakutani's). While it seems that there is no general way of proving the existence of Nash equilibria without the use of a fixed point theorem, there do however exist some (not so common in the CS literature) proofs that seem to indicate alternative proof paths, for games of two players. This note discusses two such proofs.