Learn English – “When he went out he left the radio on so that his parents shall think that he was still in the house”

modal-verbstenses

When he went out he left the radio on so that his parents shall
think
that he was still in the house.

This is a past sentence. Why is shall think used? Can I use should think?

Best Answer

Should think is technically correct, since this was the object of his action, not the consequence. Would think is so common that only pedants would object, should you use it.

Shall think cannot be correct in this situation; without more context we can't say why the author thought it might be.

Edit to support the first sentence: "Roughly, shall and should are used when the word on which the that-clause depends expresses an influence that affects the result, as a demand does, but a hope or fear does not. In 'England expects that every man will do his duty', the substitution of shall for will would convert an expression of confidence into an exhortation." Fowler (ed. Burchfield), sv 'shall and will'. The article ends by saying "But the American practice of omitting the auxiliary in such sentences is becoming increasingly common in Britain: I am anxious that... the right site be selected"; I don't know whether this really is American practice, but it is rare (though not unknown) in the British circles I move in.