if條件句虛擬語氣不同時態的辨析(if had used, if could have used)

書上原句：（海明威老人與海）

a) If I could have used a bat with two hands, I could have killed the first one surely. （虛擬語氣）

如果我可以用雙手掄起一根棒球棒，我準能把第一條鯊魚打死。



我疑惑的是為何原句a)中if條件句用了could have used ? 怎么樣理解？



假如把could have used改成had used,如下b)句：

b) If I had used a bat with two hands, I could have killed the first one surely.



意思有變化嗎？



a) If I could have used a bat with two hands, I could have killed the first one surely.

b) If I had used a bat with two hands, I could have killed the first one surely.

兩句都對，意思略有差別。

第一句比第二句，多了一層意思“可以”。could 表示“能力”。

哪個告訴過你，if 從句不可以用 could？用might 也可以。

if 從句中，had used 和 could have used 分別表示“過去未做到” 和 “過去未能做到”。后者比前者多了一個“可以”。其他都一樣。

我再用 could 舉一個例子：

If he could come, we would not go out.

假如他可能來的話，大家就不走了。

意思是：他來的可能性極小。這是與“以后” 不符的虛擬語氣。

以下說法，都可以：

If he came, we would not go out.

If he could come, we would not go out.

If he might come, we would not go out.

If he should come, we would not go out.

If he were to come, we would not go out.