There are two main themes that appear to be suggested in the first chapter of this classic coming-of-age novel. Firstly, the hypocrisy of Christianity and secondly the importance of superstition.
Notice how the hypocrisy of Christianity is introduced. As part of her attempt to civilise Huck, the Widow Douglas tries to teach Huck various Bible stories. However, when he discovers that characters such as Moses had been "dead a considerable long time," Huck loses interest, because he doesn't "take stock in dead people." When he tries to smoke, he is told off by Widow Douglas because it was "a mean practice and wasn't clean." Huck is ironic about the contradiction that he sees between her character and her actions:
Here she was a-bothering about Moses, which was no kin to her, and no use to anybody, being gone, you see, yet finding a power of fault with me for doing a thing that had some good in it. And she took snuff, too; of course that was all right, because she done it herself.
Thus the hypocrisy of Christianity is symbolised in the way that Widow Douglas won't let Huck smoke but herself takes snuff.
Likewise superstition is presented when Huck, feeling scared at night, accidentally kills a spider when he flicks it into a candle flame:
I didn't need anybody to tell me that that was an awful bad signand would fetch me some bad luck, so I was scared and most shook the clothes of of me. I got up and turned around in my tracks and crossed my breast every time; and then I tied up a little lock of my hair with a threat to keep witches away.
Huck clearly lives in a world full of omens and signs and feels the need to protect himself from these things. The importance of superstition in the novel as a whole is a theme that is returned to again and again, especially through the way that Jim places so much emphasis on superstition.