Expressões em inglês quando você discorda com alguém

1. I'm not sure about that! (Phrase 1 is a brief expression for saying that you don't have an opinion. Because of its brevity it might seem a bit rude.)
2. You could be right, but... (Phrase 2 indicates (in a fairly polite way) that you don't think the question is very interesting because you never think about these things.)
3. (I'm afraid) I don't agree.(I'm afraid) I don't agree. (Phrase 3 might be an answer to a question about what somebody is going to do. you are saying that you don't really care.)
4. I agree up to a point, but.. 
5. That's an interesting idea, but..(Phrases 4 and 5 are saying that you don't have enough information to answer a factual question.)
6. Do you really think..? (Phrase 6 is similar to phrase 1. It is saying that you have no opinion or idea about something.)
7. Rubbish! / Nonsense!
8. You can't be serious!
9. Actually, as a matter of fact. I think.(Phrases 7, 8 and 9 are saying that you are not affected by the topic of the question and so have no opinion or interest in the topic.)
10. That's not how I see it. (Phrase 10 is often used by politicians. Although they say that the question is interesting)