What do Mrs. Bedwin and Mr. Grimwig argue about at the end of Chapter 17?

Mrs Bedwin and Mr Grimwig argue about whether or not Oliver is an imposter;

"'I never will believe it, sir,' replied the old lady, firmly.

'Never!'

'You old women never believe anything but quack-doctors, and

lying story-books,' growled Mr. Grimwig. 'I knew it all along.

Why didn't you take my advise in the beginning; you would if he

hadn't had a fever, I suppose, eh? He was interesting, wasn't

he? Interesting! Bah!' And Mr. Grimwig poked the fire with a

flourish.

'He was a dear, grateful, gentle child, sir,' retorted Mrs.

Bedwin, indignantly. 'I know what children are, sir; and have

done these forty years; and people who can't say the same,

shouldn't say anything about them. That's my opinion!'

This was a hard hit at Mr. Grimwig, who was a bachelor. As it

extorted nothing from that gentleman but a smile, the old lady

tossed her head, and smoothed down her apron preparatory to

another speech, when she was stopped by Mr. Brownlow."