[Grammar] I'm not sure that/whether she is honest.

[wotcha]

1.I'm not sure that she is honest.

2. I'm not sure whether she is honest.

3. I'm sure that she is honest.

4. I'm sure whether she is honest.


I want to know if there any differences between 1 and 2.

Also I wonder if 4 makes sense - and grammatical.

 

[BobK]

1 is good. 2 would be accepted by many people (chiefly by people who don't recognize a relation between whether and either - so I would prefer 'I'm not sure whether she is honest or dishonest'). 3 is fine. 4 makes no sense.

b