“Mountain climbing can be very dangerous. You can’t be too careful.”

No matter how careful you are, it isn’t too careful. It’s impossible to be too careful. In some contexts, though, this phrase can have almost the opposite meaning.

“Jim is very sensitive. You can’t be too gentle with him, or you’ll hurt his feelings.”

“Bob is very insensitive. You can’t be too gentle with him, or he won’t listen.”

With Jim, no matter how gentle you are, it won’t be too gentle. “You can’t” means “It’s impossible” here. With Bob, you shouldn’t be too gentle. “Can’t” means “shouldn’t” this time.





ジムの場合は、いくら優しくても優しくしすぎるということにはなりません。「You can’t」は「不可能だ」の意味です。ボブの場合は優しすぎることを避けるべきです。この「can’t」は「shouldn’t」と同じ意味で使われています。