The rule is that a convert not only cannot be sought out, but must be strongly discouraged at least 3 times from converting - that's how you make certain that the conversion is legit.
Had Gaarder read his Bible...
He probably doesn't even have one, and I rather doubt that he believes in anything higher than man, government or race.
Aha, there's that number 3 again!
3 discouragements
3 rabbis
3 things the convert must do