Expression "unless he be a lunatic"

[Sitifan]

1. No one, unless he be a lunatic, would do that.
2. No one, unless he should be a lunatic, would do that.
3. No one, unless he is a lunatic, would do that.
4. No one, unless he were a lunatic, would do that.
Which of the above sentences is NOT acceptable?
_________________
Thank you very much for your reply.

[Diverhank]

What about "No one except a lunatic, would do that" ?

[Mister Micawber]

.
Of your 4 sentences, only #3 does not present a hypothetical lunatic.
.
_________________
Native English teacher at Mister Micawber's

[Sitifan]

[Mister Micawber]

.
#3 is quite common, but if this is a test question, then it is the unacceptable one. Strict grammar asks for the hypothetical here because of the 'would do' conditional.
.
_________________
Native English teacher at Mister Micawber's

[Nessie]

Hi MM,
could you please be a bit more detail about your explaination?

1/ Can 'unless' be used with the same structures as IF (3 types)?
2/ Except #4, I find the other three sentences a bit strange... could you explain the difference among them?
3/ What's the difference between the version 'No one, unless he were a lunatic, would do that' and the version 'No one, unless he is a lunatic, do that'?

Many thanks in advance,
Nessie.
_________________
:(... something we never have again, I know... I guess I really really know.. :(

Sorry seems to be the hardest word...