Complementation by finite clauses
Adjectives which take embedded that- clauses indicate the speaker’s or writer’s stance with respect to what is expressed in the complement. Semantically, they fall into two main types:
degrees of certainty, such as: sure, certain, positive, convinced
affective meanings, such as: glad, sorry, happy, sad, afraid, grateful, pleased, amazed, annoyed
After some adjectives of emotive or modal meaning, such as anxious, willing, eager, insistent, determined, essential, the non-factual auxiliary should (in Br E), or the subjunctive (especially in Am E), can be used in the that-clause to suggest a present or future action. An indicative is used by some speakers, as in 3.
1 The public is anxious that the truth should be known (BrE)/be known (AmE).
2 We are not willing that justice should be forgotten(BrE)/be forgotten(AmE).
3 Bill’s wife is insistent that he give/gives up smoking.
Certain adjectives such as clear can take a wh- complement clause, as in:
It is not clear what you mean.