Oh, another thing: I remember thinking that it didn't make sense to favour either the many worlds interpretation or the copenhagen interpretation, because no empirical fact we could collect could point towards one or the other, being as we are stuck in just one universe and unable to observe any others. Whichever one was true, it couldn't possibly impact on one's life in any way, so the question should be discarded as meaningless, even to the extent that it didn't really make sense to talk about which one is true.

This seems like a basically positivist or postpositivist take on the topic, with shades of Occam's Razor. I was perhaps around twelve. (For the record, I haven't read the quantum mechanics sequence and this remains my default position to this day.)