Why is it that ～かねる can refer to oneself, yet ～かねない must refer to another person?


When I tried to use ～かねない to express my own feeling about a situation, I was
told by a native that it sounds incorrect and strange. However, ～かねる is
appropriate and fine. For example, this is the impression I get of what is
going on.

> 彼が本当のことを言っているとは信じかねる  
>  (the speaker thinks it's hard to believe he's telling the truth)
>
> 彼が本当のことを言っていると信じかねない  
>  (the speaker thinks he's probably not telling the truth, yet others think
> he is)

However, I was told that ～かねない cannot directly refer to the speaker's opinion,
but to can refer to someone else. For the second example, is it true that you
must directly reference a different party? Why is that?




Think of かねない as するおそれがある, and then think about how that would fit in with the
speaker's opinion. It would be like saying 信じるかもしれない when talking about
yourself. However, かねる simply means "cannot", so you can use it when speaking
about yourself.

I would translate your second sentence as:

> I might believe that he is telling the truth.

