If you don't expect people to do something, there is no reason to make it "illegal." But "illegal" can mean many different things. It is illegal to jaywalk, but that will only rarely get you a ticket, if that. It is illegal to murder people, and if you murder someone you may well be executed. It is not (I believe) illegal to commit adultery, but it is grounds for divorce. It is not illegal to lie, but it is frowned upon.
There is some scale of "how much punishment is appropriate for this act." Acts like lying are very hard to prosecute. Acts like jaywalking aren't very problematic. There is some amount of punishment which is ideal, and some amount of enforcement which is ideal.
When people say "people will do X whether it's illegal or not" the argument I perceive them to be making (and intended to make) is that increasing the penalties or prosecution for the crime in question will, at the margin, have a worse effect on crimes and welfare than leaving the laws constant. In part because everyone who is persecuting someone for having an abortion or smoking a joint is not trying to catch someone who has kidnapped children or committed murder, and adding more resources (at the margin) to those endeavors will be more worthwhile.
That's a fine use of the principle of charity, and I endorse it on those grounds.
And I certainly agree that in many cases criminalizing (or more harshly prosecuting already-criminal) activity has a worse effect than legalizing it, and that this is absolutely an important argument to make where relevant.
Abortion is one of the most politically-charged debates in the world today - possibly the most politically charged, though that's the subject for another thread. It's an excellent way of advertising whether you are Green or Blue. As a sceptical atheist who thinks guns should be banned and gay marriage should be legalised, I naturally take a stance against abortion. It's easy to see why: a woman's freedom is less important than another human's right to live.
Wait... that sounds off.
I really am an atheist, with good reasons to support gun bans and gay marriage. But while pondering matters today, I realised that my position on abortion was a lot more shaky than it had previously seemed. I'm not sure one way or the other whether a mother's right to make decisions that can change her life trumps the life of a human embryo or fetus. On the one hand, a fetus isn't quite a person. It has very little intelligence or personality, and no existence independent of its mother, to the point where I am comfortable using the pronoun "it" to describe one. On the other hand, as little as it is, it still represents a human life, and I consider preservation of human life a terminal goal as opposed to the intermediate goal that is personal freedom. The relative utilities are staggering: I wouldn't allow a mob of 100,000 to kill another human no matter how much they wanted to and even if their quality of life was improved (up to a point). So: verify my beliefs, LessWrong.
If possible, I'd like this thread to be not only a discussion about abortion and the banning or legalisation thereof, but also about why I didn't notice this before. For all my talk about examining my beliefs, I wasn't doing very well. I only believed verifying my beliefs was good; I wasn't doing it on any lower level.
This post can't go on the front page, for obvious reasons: it's highly inflammatory, and changing it so as not to refer to a particular example would result in one of the posts I linked to above.