ないことはない・
Two negatives make a weak yes: "I can, I suppose", "it's not that I don't". You grant that it is possible, or true up to a point, and hold back a wholehearted yes. A "but" usually follows.
I can eat it, I suppose, but it's not a taste I like much.
I can see how he feels, up to a point, but I can't agree with the way he said it.
ないことはない
ない-form + ことはない
行けない → 行けないことはない; おいしくない → おいしくないことはない; 便利ではない → 便利ではないことはない.
なくはない
ない-form (ない → なく) + はない
行けなくはない, おいしくなくはない. Shorter, with the same force. In both, は can be も: ないこともない, なくもない.
- Before it
- A negative. Most often 分からない or a "can't" (行けない, できない, 食べられない), or an adjective.
- After it
- が or けど and the catch. Often the sentence just stops at けど….
- Tone
- Lukewarm: a yes with strings attached.
- Where you'll meet it
- Conversation above all; reviews and opinion pieces too.
In use
Can you help with the move on Saturday?
I could, but only in the afternoon.
This dish isn't bad, but it's not so good that I'd order it again.
You could walk from the station, but with a lot of luggage the bus is better.
I could go, I guess, but I'm a bit tired today.
With も it is the same weak yes.
A weak yes, not a strong one
The two negatives you know from 行かなければならない, "I must go", are strong. These are not: they usually come out weaker than a plain yes.
I could go tomorrow, I suppose.
A weak yes. Something is holding you back.
So an answer like 行けないことはないけど… is not "sure": the person is hanging back. For a glad yes, people say it straight: 行けます.
Close neighbours
ことはないN3
After the dictionary form, with no negative in front, the same words are "no need to".
There's no need to worry about it all by yourself.
ことは～がN3
The same word twice: a full yes to the bare fact, then the "but".
I did watch the movie, but I fell asleep several times during it.
わけではないN3
"It's not that…": you take back a conclusion the other person might jump to. Often it means "not entirely".
I chose the online course, but that does not mean I dislike learning in a classroom.
The same weak yes, stiffer; 分からないでもない and 気がしないでもない are everyday. ないものでもない, "I might, if…", is bookish.
I can understand her decision up to a point, but I can't agree with it.
Check yourself
1What is B saying?
A
Choose an answer to see why.
2Which one is the weak yes?
Choose an answer to see why.
More sentences
I can sort of see how you feel, but I still think you'd better not.
This job is enjoyable enough, but it's pretty tiring.
If you hurry now you might just make it, but I can't promise.
This area is convenient enough, but there are few buses at night.