Understanding 警戒と注意<に>

Question

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.

Answer 1

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.