【问】 So bright was the moon that flowers were bright as by day. (Mansfield)

请问这里为什么要主谓语倒装?

【答】 按照英语惯用法，在so... that+结果(程度)从句这一结构里，如果充当表语的so+形容词或充当状语的so+副词放在句首，则主句的主语和谓语要进行部分倒装。例如：

1. So sudden was the attack that we had no time to escape. (PEG)

袭击来得非常突然，以致我们都来不及逃跑。

2. So absorbed was he that Nathalie hadn't dared to make a sound.

他是那样全神贯注，以致纳塔莉没有敢出声。

3. So simple does the trick seem that we are likely to overlook the magician's dexterity.(IME)

戏法似乎太简单，以致于我们很有可能忽略魔术师的技巧。

4. So earnestly did the boys beg that their father gave his permission. (IME)

男孩儿们恳求得如此热切，结果父亲同意了。

(参见so¹)