[quote:6e6d6e7a5b="Rincewind"]What do you mean by burning it as an act of faith? For me, though, the idea was inspired by the book, it was more an act of practicality-he needed something that could burn? [/quote:6e6d6e7a5b]
You're sort of getting at what I meant in your second paragraph. Oats realises that what his faith is [i:6e6d6e7a5b]about[/i:6e6d6e7a5b] is not the book, but [i:6e6d6e7a5b]doing[/i:6e6d6e7a5b] the things in the book. The book tells you how to live.

Burning a book is normally an act of defiance against its contents. But in this case, it is a confirmation and validation of the book's contents. Oats is making the preservation of human life more important than the preservation of religious structure - which is exactly what post-Brutha Omnianism is all about. Or should be. That is the realisation Oats makes, thanks to Granny, and that is what he is confirming through his action.

Burning the book is an act of faith because it is a confirmation of what he believes in; he is recognising the book as having the power to save lives at the most practical level. He is seeing that what he believes in is more than just a pile of paper, and that it therefore doesn't matter if the paper burns, because what he believes in will still remain. It is also a confirmation of a more Granny-style belief; do the best you can with what you've got, even to the extent of doing the unthinkable.

Burning the book is a statement of belief in all these things. That is why it's an act of faith, rather than a denial of faith.

(And, by the way, discussing fictional theology is geeky.)