学员疑问：There is no science but tells a different tale, when viewed as a portion of a whole, from what it is likely to suggest when taken by itself, without the safeguard, as I may call it, of others. 老师，这句but 和这个tell怎么理解成分构成呢？

老师解答：but在英语句子中可用作关系词，引导定语从句，但它虽然形式上是肯定的，意义上却是否定的，相当于which/that/who+not。因此，There is no science but tells a different tale 相当于 There is no science that doesn't tell a different tale 简而言之是 Every science tells a different tale。

点评分析：这是定语从句的一些特殊引导词，可以多结合几个例子理解：

There is no rule in English but has exceptions.（英语中没有无例外的规则）相当于  There is no rule in English that doesn't have exceptions. 简而言之是 Every rule has exceptions.

There is no old habit but may be cured by a strong will power.（通过强大的意志力没有改变不了的旧习惯）相当于There is no old habit which may not be cured by a strong will power.简而言之是 Every old habit may be cured by a strong will power

There is nobody but has his faults. (金无足赤，人无完人。)相当于There is nobody who doesn't have his faults.简而言之是 Everybody has his fault.