Try rewriting the lecture as a formal essay and examine Forster’s statement: ‘…since the novel is itself often colloquial, it may possibly withhold some of its secrets from the graver and grander streams of criticism’.

Forster’s statement, ‘since the novel is itself often colloquial, it may possibly withhold some of its secrets from the graver and grander streams of criticism’ talks about how novel deals with the colloquial aspects of life and is written in a colloquial language so that it becomes accessible to humbler people too. Therefore, neither would it have the characteristics of a formal essay nor would it deal with higher or more philosophical subject matters that can be subject to ‘grander’ criticisms.