] ] I noticed this line in P2, which I believe was spoken by Lady Russell.

There were not many who were serious atheists in public. It wasn't good for social promotion. David Hume wanted his essay against the logical possibilty of miracles to be published after his death. And he is often sited as an atheist but he really can't be proven as such.

Atheism wasn't good for you popularity.

] One clue, if it helps, is the opening line in this exchange when Lady Russell asks, "Did you attend the Philosophical Society?" Whether this would be a discussion group or an organized debate I don't pretend to know, but it does seem to be an event at which ideas are exchanged with spirit, rather than a straight lecture.

I always took this discussion to be about a sort of entertainment. One side tries to prove the other side is wrong. Like the silly debates debating clubs have "Be it resolved that the Marvel universe is the better comic book fantasy world" - that sort of entertainement/silliness.

The people debating would not be expected to really hold the heretical belief of Atheism. It would merely be an excersize in showing you are a smarty pants or watching others showing off. It might be fun to set up a debate where one side tries to do the impossible - show that Atheism is rationally based. And thought this is the age of Empiricism, even most Empiricists still clung to the need to have logical proofs to back up their beliefs.

Berkley commented about how God allows one to be sure objects remain even when we are not there to percieve them - because God is always there percieving everything.

There is a strong thread of religious themes and thought in 19th century philosophy. (and actually there still is...)