Things are starting to get interesting! After the fight with the goblins, Bilbo gets separated from the group and wakes up in Gollum's cave. There were a few things that I noted while reading, though I didn't listen to the lecture this week and I'm not a long-time Tolkien person so my interpretations could be off.
I remember hearing that later in the series you find out that Gollum actually used to be a Hobbit and has been twisted by the darkness and loneliness into the creature that he is. I picked up on a hint here and there, the most telling being-
"...Gollum brought up memories of ages and ages and ages before, when he lived with his grandmother in a hole in a bank by a river..."
Gollum hasn't always been this way, and it seems like somewhere deep down Bilbo knows that. He feels empathy for him even though Gollum wants to kill him.
Again Tolkien uses something silly to make a very grim situation a little bit more "kid-friendly". Gollum is scary, he carries around goblins teeth and a stone to sharpen his fangs on in his pockets, he scampers around in the dark and snatches goblins and whatever else he can find to eat. It's pitch black and Bilbo is hopelessly lost. The riddle game, "sacred and of immense antiquity" distracts from the desperation of the situation and leads to a couple of funny moments. My favorite was when Bilbo said "The answer's not a kettle boiling over, as you seem to think from the noise you are making."- it sort of shows that he's becoming more brave in the face of danger.
I like that the great ring of power enters the story in such a nonchalant way. Bilbo wakes in the darkness, gropes around and there it is. And he proves he is worthy of it immediately by not killing Gollum when he has the chance.
"He must stab the foul thing, put its eyes out, kill it. It meant to kill him. No, not a fair fight. He was invisible now. Gollum had no sword. Gollum had not actually threatened to kill him, or tried to yet. And he was miserable, alone, lost."
The last thing I wanted to mention is what seems to me like a brief reference to evolution. I don't know very much about Tolkien's personal beliefs aside from knowing he had an interest in theology that's reflected in LOTR, but I was pleased to see this passage. Not only because I like seeing people be interested in both science and religion but also because it's just wonderfully descriptive:
"Still he did not dare to wade out into the darkness. He could not swim; and he thought, too, of nasty slimy things, with big bulging blind eyes, wriggling in the water. There are strange things living in the pools and lakes in the hearts of mountains: fish whose fathers swam in, goodness only knows how many years ago, and never swam out again, while their eyes grew bigger and bigger and bigger from trying to see in the blackness; also there are other things more slimy than fish."
It's also worth noting that Bilbo got himself out of trouble this time and that he seems to be a bit more comfortable with adventuring- for example, upon finding himself lost in the dark he at first tries to smoke his pipe, which is a pretty chill reaction. And once again it's wit and a bit of luck that saves him, not violence.
Favorite quote from the chapter: "Go back?" he thought. "No good at all! Go sideways? Impossible! Go forward? Only thing to do! On we go!"
[I was going to combine Ch. 5 & 6 into one post but this ended up taking longer than I thought after gathering the pictures and everything. So here's a very late Ch. 5, still gotta go back and read everyone else's posts, and then Ch. 6 will be up later!]