Would you open the window? →過去形にしたら丁寧なのではなく、仮定法の一種。
【現在】仮定法過去:If S 過去形 , S would 原型 過去形を使うってだけで、意味は現在。 If I were 〜 I でもwere を使ってめちゃくちゃな 【過去】仮定法過去完了:If S had p.p. , S would have p.p If cleopatra's nose had been shorter, the whole face of the earth would have changed.(パスカル) If S should 原形 , 命令文 など(万が一) If S were to 原形 , S would 原形(完全妄想)