In Grammar^x, Modal auxiliaries^x, Constructions^x

Anonymous wrote I have seen similar putative sentences I am suprised that he should feel lonely 1 I am suprised that he feels lonely I don t remember the exact sentences in Quirk s A Comprehensive English Grammar I wonder if the first sentence can be written as I will be suprised that he should...

I think here let is a modal auxiliary and except for ought to they are followed by a bare infinitive You ll find the same construction after help make causative and perhaps others but I don t know the explanation for it just that it s a grammar rule