Understanding 警戒と注意<に>


> 士道は真剣な表情でうなずきかえした。それはそうだ。士道は六喰に幾度となく殺されかけているのである。警戒と注意 **に**
> 、し過ぎということはないだろう。

I understand the last sentence means he can’t be too careful. But how should I
make sense of this bold に? If it was を, then it’s easier to understand.




As noted in the comment, this に can be understood as the common place
indicator and 警戒と注意 as an abstract place. Essentially it means the same as
に関して here. So literally, _In the realm of caution and attention, doing too
much does not exist_.

Using を is possible, but then inserting a comma looks odd. It should be
警戒と注意をしすぎということはないだろう. This is probably because the verb-object relationship is
felt stronger than topic-verb relationship in case of using に.

