'So so,' rejoined [Gowan]. 'To be candid with you, tolerably. I am not a great impostor. Buy one of my pictures, and I assure you, in confidence, it will not be worth the money. Buy one of another man's--any great professor who beats me hollow--and the chances are that the more you give him, the more he'll impose upon you. [...] Give almost any man I know ten pounds, and he will impose upon you to a corresponding extent; a thousand pounds--to a corresponding extent; ten thousand pounds--to a corresponding extent. So great the success, so great the imposition. But what a capital world it is!' cried Gowan with warm enthusiasm. 'What a jolly, excellent, lovable world it is!'
'I had rather thought,' said Clennam, 'that the principle you mention was chiefly acted on by--'
'By the Barnacles?' interrupted Gowan, laughing.
'By the political gentlemen who condescend to keep the Circumlocution Office.'
'Ah! Don't be hard upon the Barnacles,' said Gowan, laughing afresh, 'they are darling fellows! Even poor little Clarence, the born idiot of the family, is the most agreeable and most endearing blockhead! And by Jupiter, with a kind of cleverness in him too that would astonish you!'
'It would. Very much,' said Clennam, drily.
'And after all,' cried Gowan, with that characteristic balancing of his which reduced everything in the wide world to the same light weight, 'though I can't deny that the Circumlocution Office may ultimately shipwreck everybody and everything, still, that will probably not be in our time--and it's a school for gentlemen.' (1.26.47-54)
Gowan here spells out some of his philosophy – basically that everything good is only average, and everything bad is pretty much OK. His fake honesty about his own flaws ("buy one of my pictures and it will not be worth the money") seems at first charming and self-deprecating. But since he does this about everything, it's really just a handy way to mask the major disappointment of his life – himself.