Levitt points out that while there is agreement about most activities considered criminal - like murder, rape or robbery - there are also some activities like gambling, prostitution and recreational drugs over which there is still controversy. Levitt adds that he is never sure what shapes his decisions about which of these activities should be illegal:
Not that my opinion matters at all, but despite strong economic arguments in favor of drug legalization, the idea has always made me a little queasy. Conversely, although logic tells me that abortion as practiced in the U.S. doesn’t seem like such a great idea... something in my heart makes me sympathetic to legalized abortion.
I came to realize that the primary determinant of where I stand with respect to government interference in activities comes down to the answer to a simple question: How would I feel if my daughter were engaged in that activity?
If the answer is that I wouldn’t want my daughter to do it, then I don’t mind the government passing a law against it. I wouldn’t want my daughter to be a cocaine addict or a prostitute, so in spite of the fact that it would probably be more economically efficient to legalize drugs and prostitution subject to heavy regulation/taxation, I don’t mind those activities being illegal.
On the other hand, if my daughter had good reasons to want an abortion, I would want her to be able to have one, so I’m weakly in favor of abortion being legal, even though I put a lot of value on unborn fetuses.
If you listen carefully you'll hear the sound of Steven Levitt's point soaring, gracefully undetected, over the heads of his critics. Levitt wasn't using the 'daughter argument' as a good way to decide what activities should be prohibited.
Instead he was simply showing some healthy introspection. Levitt recognised that his stances on political issues were being determined, not by reasonable contemplation, but by an emotional attachment to and concern for his daughter. He's not saying that this is good, he's saying only that this is how his mind works.
We're all emotional beings and we are all prone to biases that interfere with rational thought. That Levitt acknowledges his personal bias or blind spot in public is a very healthy thing, and it shows that he is capable of challenging his own prejudices.