28. Certainty and uncertainty, ignorance

A. Certainty

Certainty in reply to a question, or in agreeing with a statement, can be expressed as follows:

Yes, it/he is. No, it/he isn’t

Yes, certainly No, certainly not

Yes, it/he certainly is. No, it certainly isn’t

(Yes,) definitely. (No,) certainly not

Definitely is slightly stronger than certainly, implying that there is no doubt, and is more common in informal conversation.

I’m (quite/ absolutely) sure/ certain.

Sure is more common than certain in informal conversation. Note also that to be sure is much more common than to know for sure.

I am sure/ certain of it/ that / that…

There is no doubt about it/that.

Be careful of no doubt used adverbially, and doubtless. In colloquial style they often mean little more than probably, I think/ suppose.

B. Uncertainty

I am not sure/ certain.

I am not quite / at all sure/ certain.

Here at all expresses a greater degree of uncertainty than quite.

I cannot/ couldn’t say (for sure/ certain)

I think so. – strong stress on think.

These may also be used when one knows something but does not wish to seem dogmatic:

As far as I know.

If I remember rightly.

If I’m not mistaken.

C. Ignorance

I don’t know.

I really don’t know. – more emphatic. Really is not stressed here.

I don’t know, I am afraid. more

I am sorry, I don’t know. Polite

I wouldn’t know – casual

I can’t remember.

I can’t/ couldn’t say.

I’ve no idea.

Sorry, I’ve no idea – more polite

I haven’t the faintest idea. – emphatic

I have not a clue – same meaning, more colloquial.

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