But is has another sense which is not a rhetorical sense, because metaphor is sort of the heart of rhetoric, the rhetorical sense A is B--when, by the way, A we know perfectly well that A is not B. How can A be B? A is only A.

但是is有另外一个意思，修辞之外的一种意思，因为暗喻差不多可以说是修辞的中心，修辞中所说的A是B，顺便说一下，我们十分清楚地知道A不是B，A怎么能是B呢，A就是。

耶鲁公开课 - 文学理论导论课程节选