Raphael is saying, with angelic circumlocution, that knowledge without wisdom, limitless knowledge, is not worth a fart; he is not a humorless archangel.
To do so, he felt, would show a lack of intelligence. For advice, he depended on close friends. These were the men with whom he had served during the Civil War.
In his younger days—for, after all, there was a dim tradition that he had been, not young, but younger—Uncle Venner was commonly regarded as rather deficient, than otherwise, in his wits.
Whereas book smarts, a person can graduate with a PhD, and then go out into the real world to work and not know what's going on because this person lacks street smarts.
There is every reason to suppose that he desired to make a good impression; and if he fell short of this result, it was not for want of a good deal of intelligent effort.
Mr. Farebrother contended on theory for the desirability of all games, and said that Englishmen's wit was stagnant for want of them; but Lydgate felt certain that he would have played very much less but for the money.