How stupid is he to believe such nonsense?

[navi tasan]

Which are correct?

1) How stupid is he to believe such nonsense?
2) How stupid should one be to believe such nonsense?

3) How stupid is he in order to believe such nonsense?
4) How stupid should one be in order to believe such nonsense?

 

[jutfrank]

The first two.

The to-infinitive there is not about purpose, so 'in order to' isn't right.

 

[Skrej]

'Should' sounds wrong to my ear. I'd expect 'must' if otherwise maintaining the original structure.

The most natural to my ear is 'does he/one have to be', or 'do you have to be' but that's changing the original structure a bit.

 

[jutfrank]

'Should' sounds wrong to my ear. I'd expect 'must' if otherwise maintaining the original structure.

Although it's perfectly grammatical (which I think is what the OP is asking about), I agree that 'should' doesn't make good sense here, and is probably not what navi tasan means.

Navi, please make it clear what you're really asking. What do you mean by 'correct'? What are you trying to say? It's often very hard to understand what your questions are really about.

 

[navi tasan]

Thank you both very much,

It is supposed to be a rhetorical question. The idea is that someone must be extremely stupid to believe that nonsense.

And, yes, you are correct. 'Should' doesn't work. It should be 'must'. I wasn't paying any attention to that because I was thinking about 'in order to'.

Gratefully,
Navi

PS. There was a typo in the question. I corrected it. The 'be' in '4' was in the wrong place.

 

[emsr2d2]

In natural BrE, I'd say "How stupid does he have to be to believe that nonsense?!"