Anticipating resentment of my taking too much space in Q&A. here is a second item
from The Vocabula Review archive, which I hope may elicit comment:
"3. doubt that Misused for doubt whether. " Although I never fail to sympathize with the general concern, I doubt that it's possible to engineer a
happy return to a world in which secrets could be kept."

USE doubt whether. [Harper's]

To me, "whether" always implies a comparison, a choice, and "whether or not" can be clumsy.

Please comment.

comment.

The TVR gang is a bunch of stuffed shirts that have no faith in the ability of the language to function without their shepherding.

I'm a Belle Whether. I like the word and try to use it whenever I find it appropriate. Makes me feel like I'm being oh-so-precise in this World of Shades and Shadows.

If I’ve got the hang of this, your proposition can be illustrated thus:

Take 1:

Statement: “I’m told that it is possible to engineer a happy return to a world in which secrets could be kept.”
Response: “I doubt that (it's possible to engineer…).”

In this case there is no choice to be made, so ‘doubt that’ may be used.

Take 2:

Statement: “Do you think it is possible to engineer a happy return to a world in which secrets could be kept?”
Response: “I doubt whether it is (possible to engineer …).”

In this case there is a choice implicit in the question, so ‘doubt whether’ should be used.

The use of ‘whether’ in Take 2 feels clumsy. It would feel more natural to say ‘I doubt if it is’ or more simply ‘I doubt it’. I doubt if / whether / that I would normally find a need to use ‘doubt whether’ except when choices were distinctly stated as in, for example: “I have some doubt whether he will go east or west”. Even that is ambiguous as it leaves other alternatives available such as carrying on south. “I doubt whether he will go east or west” definitely introduces further options. But then I've probably got the wrong end of the stick anyway!

I agree with Faldage; I don't believe it matters.

I have some doubt whether he will go east or west

This seems incredibly imprecise if the choices are east or west. It seems to imply that the doubt is about whether he will go at all. Precision would require that one say, "I am unsure as to whether he will choose to go east or go west," or some such vebose gobbitch.

Absolutely. As I said: for example: “I have some doubt whether he will go east or west”. Even that is ambiguous as it leaves other alternatives available such as carrying on south.

I think you have to be careful when using 'doubt whether'.