The ethics of abortion is a topic that really interests me. Having two kids changed my perspective on a lot of things. I’m not exactly sure when my intellectual journey on abortion started, but I can share two arguments against abortion that have pretty much persuaded me that abortion is wrong in the vast majority of cases.
While many are convinced that the debate boils down to a question of whether the fetus is a person, both arguments against abortion I will present sidestep that question altogether. Neither argument requires the assumption that fetuses are persons (though I take it as obvious they are human). I consider that a strength of the two arguments.
#1: A Future Like Ours
The Wrongness of Killing
Many experts on the abortion debate recognize that the “Future Like Ours” argument from Don Marquis is one of the strongest arguments against abortion to date. It starts with a simple question: why is killing wrong?
Some answer this question by saying that causing pain and suffering is wrong. But this doesn’t explain why it’s wrong to kill. Some deaths are relatively quick and painless. Also note that appeals to the anguish of family members and friends won’t work, since it’s no less wrong to kill a homeless person in their sleep than it is to kill a young child (see ). Another attempt at explaining the wrongness of killing says that personhood is sacred. However, the value of personhood doesn’t explain why it’s wrong to kill animals, nor does it explain why it’s wrong to kill infants (if you’ve ever been up close with a newborn, they lack properties we usually associate with personhood, like consciousness).
Being dissatisfied with these answers, Marquis argues that killing is wrong because it deprives an individual of everything they will ever have or experience. In other words, it deprives them of a “future like ours” (FLO). Here’s how he puts it:
He goes on to say:
The basic idea is that a future conscious life is valuable. There are certain goods associated with it (a list could be made, but essentially they are the kind of goods that make life worth living). Moreover, and this is important, “what makes my future valuable to me are those aspects of my future that I will (or would) value when I will (or would) experience them, whether I value them now or not.” Thus, to be deprived of the goods I will or would value is what makes killing so wrong.
Marquis’ account of why killing is wrong has a number of things going for it. It accounts for why it would be wrong to kill intelligent aliens, dolphins, chimps, and the like. It also provides a simple explanation for why it is wrong to kill infants. Marquis gives several arguments in defense of his FLO theory, but instead of summarizing, I’ve linked them here for further reading.
The Argument Against Abortion
With the FLO theory in place, it’s very easy to see why abortion is wrong. Abortion is wrong for the same reasons that killing infants is wrong: it deprives an organism of a future like ours. Fetuses have FLOs for the same reasons that infants have FLOs. The argument can be summarized thusly:
(2) Abortion deprives the fetus of a valuable future.
(3) Abortion is wrong.
As you can see, the argument is remarkably simple. It’s easy to understand and very easy to share with others. Keep in mind that it does turn on Marquis’ analysis of why it’s wrong to kill. So if you plan on sharing it, make sure to learn and understand that part first.
Marquis’ argument is widely discussed in the literature. What follows are responses to the most common objections.
Objection 1: The FLO account of the immorality of abortion implies that it is less wrong to kill old people, since they have less of a future they will or would value.
Response: First, nothing about the FLO account implies that it is worse to kill young children than it is to kill older people. The account doesn’t say that futures are made more or less valuable in virtue of the kinds or amounts of good conscious experiences. Secondly, there’s no reliable method of measuring the value of a given person’s future, which would mean there’s no in principle way we could compare two distinct futures. Given this, we should adopt the convention that all murders are equally wrong. A third response is to say that the FLO account of the wrongness of killing is compatible with having additional reasons not to kill (e.g.: the admirability of one’s past behavior, being made in God’s image, and so on). So it doesn’t follow directly from the FLO account that killing older people is less wrong.
Objection 2: If FLOs are so valuable, we should never use contraceptives (and further should be having sex whenever conception is possible).
Response: Marquis considers this the strongest objection to his FLO account of the immorality of abortion. I can’t see why. As he points out, the FLO account of the wrongness of killing applies to a certain class of individuals (individuals with a FLO). The fetus clearly falls into the relevant class. They have a FLO. Sperm and eggs are distinct individuals that fall into different classes. So, if contraceptives are used, there is clearly no individual of the relevant class being deprived of a FLO and this objection fails. 
Objection 3: A cow is about to walk into a machine that will alter its brain into a sophisticated one. In short, once the cow walks toward the machine, it has a FLO. However, I have the opportunity to shut the door to the machine before the cow enters it. However, if the FLO account of the immorality of abortion is true, it would be wrong to shut the door since it would deprive the cow of a FLO. But clearly it is not wrong for me to shut the door.
Response: This objection utilizes a false inference. The inference goes something like this: “If Xs have the right to Y, then potential Xs have the right to Y.” But this inference is clearly false. Potential police officers don’t have the rights of officers, potential judges don’t have the rights of judges. The FLO account of the immorality of abortion says that Xs have the right to Y, not that potential Xs have the right to Y. The plainly false inference is not required.
Let’s move on to the second argument.
#2: The Prudential Argument
I first came across this argument from Calum Miller. Here’s how he puts it:
To illustrate, suppose you are hired to demolish a building. As project manager, you hire a team of experts to get the job done. When the time arrives to press the trigger, you ask your safety officer if she is positive there is no one left in the building. She replies, “I did a walk through last night and didn’t see anyone, but I’m not 100% sure.” It’s clear what ought to be done at this point. Given the small, but reasonable chance someone is still in the building, you ought to postpone the demolition. Going forward at this point would be morally reckless and negligent.
Likewise, since there’s a reasonable chance the unborn have a right to life, it is wrong to kill them. For the sake of continuity, let’s put this argument in premise/conclusion form as well:
(5) There is a reasonable chance that the unborn have a right to life.
(6) It is wrong to kill the unborn.
The argument is valid so it can’t be faulted on logical grounds. The question is, are (4) and (5) true? I take it that, given the demolition analogy above, premise (4) is true. If there’s a reasonable chance an organism (including the unborn) has a right to life, it is wrong to kill them.
Notice how modest of a claim (5) is. It’s not saying the unborn actually have a right to life, as the first argument says. Rather, (5) is saying there’s a reasonable chance the unborn have a right to life. One might object at this point and say that what’s reasonable is subjective. So let’s think back to the demolition illustration. What level of uncertainty would make it unreasonable to go forward with the demolition? Suppose you were 90% sure no one was inside (based on the testimony of your safety officer). That leaves a 10% chance someone is still in there. Most would postpone the demolition given this level of uncertainty (that’s a pretty big chance). But suppose your officer told you she was 99% sure. Even still, that small chance, that tiny bit of uncertainty, is enough to call it off.
Think about the level of certainty you would require. Wouldn’t you want the entire building to be walked, canvased, and thoroughly searched, before going forward? You’d need to be almost certain. Also note the kind of evidence you would require. It wouldn’t be enough to sit in your office a mile away thinking hard about it. You wouldn’t rely on intuitions. No, you’d require strong propositional evidence.
The question is, what extremely good propositional evidence is there that the unborn don’t have a right to life? Even if one isn’t entirely convinced by the first argument, it at least creates enough doubt to establish the truth of (5); there’s a reasonable chance the unborn have a right to life. It follows that both (4) and (5) are true, and abortion is wrong.
Objection 1: There seems to be a “reasonable chance” that many of the lower animals (fish, deer, cows, etc.) experience consciousness. The Prudential Argument would mean it would be wrong to kill them. But clearly it is not wrong to kill fish, for example.
Response: Putting aside the fact that vegans would welcome the conclusion that killing animals is wrong, let me make clear I’m not using “reasonable chance” as synonymous with “possible chance.” A reasonable chance is one that is not only possible, but moderately probable. Is it moderately probable that, despite all appearances, goldfish can experience the same level of consciousness as humans? Is it reasonable that goldfish are proud of their achievements, have aesthetic enjoyments, love their families, and have intellectual pursuits? While all of that is certainly possible, it’s far from reasonable.
For more on the conscious experience of animals, check this out.
Objection 2: If you drive pretty regularly, there’s a non-negligible chance that you’ll kill someone at some point in your life, but this doesn’t make driving wrong. So if there’s a fairly low chance that the fetus has a right to life, the argument doesn’t work.
Response: According to this blog post, the chances of dying in a car crash in Montana are 1/4,433. That’s the highest figure, by the way. In Washington DC, that probability is 1/32,322. But imagine that probability were, say, 1/100. That would mean you’d be likely to kill 3 people a year. Clearly, if the probability were that high, then it would be immoral to drive. The same principle applies in the case of abortion. So the question is, how probable is it that the unborn have a right to life? Keep in mind that if I’m right, this probability must be based on very strong propositional evidence. I’m inclined to think that most abortionists don’t have very good reasons or evidence in support of their views. In such cases, the argument succeeds. 
For a further study of the arguments against abortion, check out these very important resources:
- The Ethics of Abortion: Women’s Rights, Human Life, and the Question of Justice – Christopher Kaczor
- Why Abortion is Immoral – Donald Marquis
- Human Life, Action and Ethics: Essays by G.E.M. Anscombe – G. E. M. Anscombe
- Embryo: A Defense of Human Life – Robert P. George
- Abortion and Unborn Human Life – Patrick Lee
- Defending Life: A Moral and Legal Case Against Abortion Choice – Francis Beckwith