I offer this as a tentative foray into a discussion about abortion, obviously spurred by the recent SCOTUS decision, Dobbs v. Jackson. I note that I have long been convinced that as brilliant as Judith Jarvis Thomson’s contribution to the debate was, it doesn’t actually solve anything. (For more on that, see the chapter Lauren Hall and I co-authored in The Routledge Companion to Libertarianism.)
Different libertarians define their political ideology in different ways. (No surprise; different egalitarians do this, different socialists do this, different welfare liberals do this; in short, all political ideologies are multiply defined. Presumably those adopting the same name have at least a family resemblance.)
Some libertarians adopt the Non-Aggression Principle. Others adopt a view that indicates simply that individual liberty is the predominant value, never set aside to promote any other value. Others accept that natural rights are the foundation for the view. Others adopt some form of consequentialism. My own libertarianism is defined by commitment to the harm principle: no interference with an individual or consensual group is permissible except to rectify or prevent genuine significant harm.
What does this my form of libertarianism say about abortion? If the principle was only about harm to persons, abortion would presumably be clearly permissible since the fetus is not a person even though it is human. Of course, religious libertarians are likely to believe that all human life is sacred and that the intentional ending of such is necessarily wrongful. While I do not believe that, the harm principle in my view is not only about persons or humans. Genuine significant harm can occur to non-humans and merit interference, so whether or not the fetus is a person is not all that matters.
The question then is: is abortion a genuine significant harm? To clarify, I use the term “significant” to indicate that de minimis harms are not the sorts of things we interfere with (the cost of doing so may be a greater loss than the harm itself). I use the term “genuine” to indicate we are not discussing mere hurts or offenses, but hurts that wrongfully set back the interests of another (for more on this, see Feinberg or chapter 3 of my 2018). Once this is recognized, it should be clear that some abortions may well be genuine significant harms and some may not. Aborting an 8 month old fetus merely because one decided on the spur of the moment to take a world tour is, I think, wrongful. It would also be significant—ending the life of a human that could have been very good. On the other hand, aborting a 6 week old fetus because one was raped is unlikely to be wrongful and is at least plausibly less significant since at that stage spontaneous abortions are not uncommon.
Some will now likely object that what is wrongful is subjective. I basically think this is false—it is at least false if meant in anyway that is troubling for what I am saying here. People do not simply decide for themselves what is wrongful. For more on this, see this BHL post and this one.
Assume I am right thus far: some abortions are genuinely and significantly harmful and some are not. What does that mean for law? On my view, answering this means first recognizing that law is a blunt instrument and as such has to wielded carefully. Perhaps making all abortions illegal after 8 months pregnant is reasonable. Making all abortions illegal is not. If a clear set of guidelines for wrongfulness can be decided upon, perhaps laws against abortions that are wrongful would be reasonable. I can’t here work out what such a list would include, but I do think a law against aborting 8 month old fetuses reasonable. Perhaps also a law against aborting a fetus on a whim (perhaps have a 5 day waiting period). Laws requiring parental (or spousal) consent might sound good but are likely to run up against significant objections, including the real possibility of rape and incest and unacceptable familial pressure. The final list will be difficult to determine and absent a final list, jurisdictions may adopt differing lists (as SCOTUS allows).
Importantly, the jurisdiction issue is more complicated than some recognize. Philosophers have long debated what would give a government legitimate jurisdiction over a group of people. I won’t be able to delve into that here, but will simply assert that I do not believe any of the US state governments is likely to have genuine legitimacy over all people within their borders. For that reason, it strikes me as perfectly acceptable for the federal government or other state governments to aid an abortion-seeker in a state wherein they are unable to get an abortion legally. (For one way this can work, see this interesting story.)