Why do 可不 and 可不是 by themselves imply agreement?

Question

It seems a little strange that

可不 and
可不是

(by themselves) imply agreement (something like 就是). The textbook 标准教程HSK4上 has some examples, e.g.:

A: 没想到咱们毕业都已经十年了。
B: 可不是！时间过得太快了，真想大家。

I'm expecting there's an underlying reason for this I'm unaware of. Perhaps it's a rhetorical question like "Is it not?"

Question: Why do 可不 and 可不是 by themselves imply agreement?

It seems like they should both mean "but no" (i.e., disagreement). Indeed, they also mean this, e.g. (sourced from YouDao):

然而，这可不那么简单。
This will not be easy, however.

Answer 1

可不，可不是，可不是吗，可不就是吗，etc are colloquial phrases to agree what the other has just said.

I'm not quite sure of the exact underlying reason, but I echo your suspicion - perhaps it's a rhetorical question like "Is it not?".

However, we should be cautious that sometimes it can mean negation too as in the OP's example: 这可不那么简单. In this case, we read as 这可/不那么简单. If you add 就 and 吗 in the sentence: 这可不就那么简单吗，it becomes a rhetorical question, meaning Isn't it that simple=it is that simple.

So, the way to determine (negative or positive) is based on the syntax and context. If 不 goes with 可，then it's positive. If 不 goes with the other part, then it's negative.

Answer 2

可不 and 可不是 are short forms of 可不是吗/可不就是吗? it is is a rhetorical question, meaning agreement with emphasis.

But in a sentence like: 这可不简单. It is a declarative sentence， meaning "This is actually not easy ". Usually used with 然而/但是 etc. meaning disagreement with previous context.

Answer 3

From the examples in your link, you can see "可不" is not a set term, it is two adverbs "可" (able to) and "不" (not), followed by a verb or verb phrase

Example:

可不交稅 =可以不用交稅 (able to not pay tax)

可不即時作答 = 可以不用即時作答 (able to not answer right away)

Another form we see 可不 together is "可" means "actually" and "不" means "not", followed by an adjective

Example:

这件事(可)不简单 = this affair is (actually) not simple

要成功(可)不容易 = it is (actually) not easy to success

可不是 (could it be not?) functions the same as "isn't it?" in English . It is a rhetorical question (meaning it is actually a statement-- that expects the listener to agree)

Answer 4

They are not the same word, just written the same.

There are several different 可's in Mandarin.

1. "able to; can; permitted to";

2. "but; though";

3. roughly, "actually" "so";

4. roughly, "so", as emphasis (usually stressed)

   and some other ones...

Indeed it makes no sense for it to be "but not" and imply agreement. It means "isn't it so." instead.

Answer 5

I suggest you forget the link you post, I have to say there is no "可不" in Chinese. it sound like "ilik eapp le"

you cant explain[可][不][是]，[可不是,.....]at the front means [indeed....]

然而however，这this可is不not那么that简单easy。 your example is not that complicated