It's quite an interesting lecture. I get a little queasy trying to comprehend and think through the anthropic principle. The comments on the article were good, and I especially liked one from (Hugo-winner) Greg Egan. In the comments (with spoilers) to "Born on a Tuesday" (your URL includes a stray period) I observed that This would be a very peculiar understanding of what "having two children" means. Such lateral thinking can be very helpful in solving contrived puzzles, but I think we should keep our language as clear and grounded as we can when trying to figure out the real world.the answer to the first question can be 1/2 instead of 1/3 with a particular understanding of the statement. If the person "has" two children because they picked them at random from a very large supply of children, half boys and girls, and they have only looked at one child to determine that he is a boy, there is a 1/2 chance that the second child is also a boy.