seem ²

这是简单句里句子成分之间的否定的转移。它与带有宾语从句的主从复合句中的否定的转移有许多相似之处(参见 think $^{2,3,4}$ )。

I can't seem to get to sleep. 在语义上等于:

It seems that I can't get to sleep. 看来我无法入睡。

这就是说 can't 实际上是针对 get to sleep 来说的,而不是针对 seem 来说的:

I seem not to be able to get to sleep.

这种句型在语义上表示：主语所表示的人尽力想做某事，但做不到或未能做到。

1. I can't seem to do it. 我好像是干不了。

2. They can't seem to concentrate. 他们似乎不能集中精力。

除了 seem 之外, 在简单句中允许否定转移的动词还有 appear:

The baby doesn't appear to be awake. (= The baby appears not to be awake.) (CGEL) 这孩子似乎还没睡醒。