Suppose you are admitted to a hospital with stomach pains. The doctors tell you they have found a tumor in your abdomen, and that they can remove it quickly and with almost no risk. However, the tumor produces an enzyme that can cure a very rare form of blindness. About five people are currently afflicted with this disorder. The tumor must remain in your body, growing, for about a year before the enzyme is ready for harvest. At the point when the tumor is ready, it will weigh close to twenty pounds and produce a number of side effects: fatigue, back pain, swelling, nausea, as well as a large protuberance in your abdomen. Does the government have a right to force you to keep the tumor in your body until it is ready for harvest so as to provide treatment for the five blind people? What if the five blind people will die within two years if they do not receive this treatment?
Suppose that one of the most popular ways for people to bond is to play tennis by an open waterway. When young people are friendly, they often do this, married couples do it regularly, and it is considered an important meaning-bestowing aspect of interpersonal interaction and a sign of emotional closeness, though it is also tremendously fun, and can be done with even casual acquaintances, if so desired. However, a minority of the population can be afflicted with a growth on the shoulder from playing this game. Over half of the population is immune to this disorder, and has no worries when playing tennis by an open waterway. Those who are susceptible can take some precautions to prevent it, but none of them are foolproof. The growth can be quickly and easily removed if it is caught early enough, however, if left unchecked, it grows, inhibiting movement. Further, if left untreated for a year, a human infant will emerge from the growth. Is it ethically reasonable to remove the growth upon first detecting it?
Popular Metaphysics 
OK I follow the abortion metaphor in the second scenario and most of it in the first one, but where do the five blind people fit in?
Anyway my answers are no, the government doesn’t have the right to force me to keep the tumor for a year, even if it’s life or death for five people, and yes, it’s ethically reasonable to remove the growth upon first detecting it.
I feel like part of this is going over my head, though. Are those two examples meant to be connected or expose some inconsistency in a common stance on abortion? If so, how?
I guess they’re supposed to show that in a roughly morally equal situation, most people would not feel obliged to turn the rights to their body over to the government. My sense is, and I could be wrong, that much of the pro-life crowd would not accept government interference of this sort, even though they condone it when it comes to control over women’s bodies.
The blind people are rough metaphors for the fetus, at least as envisioned by the pro-life crowd and how they think about a fetus, as a human life, so the blind people would be humans who would be either benefited or saved by the tumor-carrier.
These are both obviously somewhat derivative of Judith Jarvis Thompson’s example, but I’ve found, in teaching these topics, it’s best to have a broad array of explanatory tropes handy.
OK still not sure why they have to be blind or there are five of them. Is the idea that blindness = 1/5 of a human life because it’s one of five senses? Seems like an unnecessary wrinkle.
Even in 1b when you’re killing off the blind people, you’re still comparing adult lives to a fetus, which introduces more complications in both directions. Overall I think the second example works better.
I do see your overall point. I’ve always been pro-choice but I used to think of it as mainly about differences over the definition and/or sanctity of life, and over time I’ve come to see it as primarily a women’s rights issue. But that’s less because of thought experiments and more because I can just see empirically that pro-life positions are strongly correlated with various “traditional” misogynist views.
Anyway, if I were really trying to exhaustively rebut pro lifers (and I realize you’re not), I don’t think I would do it quite this way. Your examples are more effective than the popular “How can you be pro-life and pro-death penalty?” but it’s still mainly a semantic one. Even if pro-lifers talk about “absolute sanctity” of life, that’s rarely what they really mean. They’re struggling to articulate a real moral revulsion that, while almost certainly still rooted in sexism, has much more to do with the “innocence” of the fetus, the human-not-divine agency in its death, the “naturalness” of pregnancy and parenthood …as an example of the last, I think a religious pro-lifer might react even more strongly to your pregnancy-as-illness metaphor than to the ultimate fate of the fetus. Even I twitched a little at the clinical tone of “a human infant will emerge from the growth” — as though it might not even be related to the mother?