But.[usage-but]

But. 用在doubt和help之后是多余的。

• 误：I have no doubt but that
• 正：I have no doubt that

• 误：He could not help but see that
• 正：He could not help seeing that

but作为连词过于频繁地使用，会导致规则18下所讨论的毛病。用but构成的松散句，通常可以改写成用although构成的掉尾句。

尤其别扭的是but紧跟另一个but，从而构成对照中的对照，或保留中的保留。这通过重新安排很容易改正。

• 误：Our country had vast resources but seemed almost wholly unprepared for war. But within a year it had created an army of four million.
• 正：Our country seemed almost wholly unprepared for war, but it had vast resources. Within a year it had created an army of four million.