This squib provides an account of a contrast between whether and if in English, manifested in the contrast between the grammaticality of I don't know whether or not Pat will arrive and the ungrammaticality of I don't know if or not Pat will arrive. I argue that this contrast can be explained if we assume that whether can pied-pipe, but there is no pied-piping in if-questions. Strikingly, once we eliminate the pied-piping parse for whether, it behaves like if. Then I show that this contrast exists cross-linguistically: Polish alternative questions behave like whether-questions because pied-piping is possible, and Bengali alternative questions behave like if-questions because of the unavailability of pied-piping.

中文翻译：

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为什么*是否？✓

这个问题说明了英语是否与否之间的对比，这体现在我不知道帕特是否会到达的语法和我不知道帕特是否会到达的不语法之间的对比。我认为，如果我们假设是否可以进行管道传输，而在if问题中没有管道传输，则可以解释这种对比。令人惊讶的是，一旦我们消除了是否为管道着色的解析，它的行为就好像是。然后，我证明这种对比在语言上是存在的：波兰替代问题的表现是否像是问题，因为可能存在管道问题；而孟加拉语替代问题的表现像是if问题，因为没有管道问题。