While terraforming and abortion are both subjects of moral debate, they would seem to have little else in common. However, some moral arguments used to justify abortion can be used to justify terraforming.

Briefly put, terraforming is the process of making a planet more earthlike. While this is still mostly science fiction, serious consideration has been given to how Mars, for example, might be changed to make it more compatible with terrestrial life. While there are some moral concerns with terraforming dead worlds, the major moral worries involve planets that already have life—or, at the very least, potential for the emergence of life. If a world needs to be terraformed for human habitation, such terraforming would almost certainly be harmful or even fatal for the indigenous life. While it can be argued that there might be cases in which terraforming benefits the local life, I will focus on terraforming that exterminates the local life. This could be called terminal terraforming.

One way to look at terminal terraforming is as analogous to abortion. As will be shown, there are some important differences between the two—but for now I will focus on the moral similarities.

One stock argument in favor of the moral acceptability of abortion is the status argument. While these arguments take various forms, the gist is that the termination of a pregnancy is morally acceptable on the grounds that the woman has a superior moral status to the aborted entity (readers are free to use whichever term they prefer—I try to use neutral terms to avoid begging the question). This argument is very similar to that used by St. Aquinas and St. Augustine to morally justify killing plants and animals for food. Roughly put, they argued that humans are superior to animals, so it is acceptable for us to harm them when we need to.

This argument can justify terminal terraforming: if the indigenous life has less moral status than the terraforming species, then it could be argued that the terraforming is morally acceptable. The status argument has many variations. One common version uses the notion of rights—the rights of the woman outweigh the rights (if any) of the aborted entity. This is because the woman has a superior moral status. This argument is also commonly used to justify killing animals for food or sport—while they (might) have some rights, the rights of humans’ trump those of animals.

In the case of terraforming, a similar appeal to rights could be used to justify terminal terraforming. For example, if humans need to expand to a world that has only single-celled life, then the rights of humans would outweigh the rights of those creatures.

Another version uses utilitarianism: the interests, happiness and unhappiness of the woman is weighed against the interests, happiness and unhappiness of the aborted entity. Those favoring this argument note that the interests, happiness and unhappiness of the woman far outweigh that of the aborted entity—usually because it lacks the capacities of an adult. Not surprisingly, this sort of argument is also used to justify the killing of animals. For example, it is often argued that the happiness people get from eating meat outweighs the unhappiness of the animals they consume.

As with the other status arguments, this can be used to justify terraforming. As with all utilitarian arguments, one must weigh the happiness and unhappiness of the involved parties. If the life on the planet to be terraformed has less capacities than humans in regard to happiness and unhappiness (such as world whose highest form of life is the alien equivalent of algae), then it would be morally acceptable for humans to terraform that world. Or so it could be argued.

The status argument is sometimes itself supported by an argument focusing on the difference between actuality and potentiality. While the entity to be aborted is a potential person (on some views), it is not an actual person. Since the woman is an actual person, she has the higher moral status. The philosophical discussions of the potential versus the actual are rather old and are a matter of metaphysics. However, the argument can be made without a journey into the metaphysical realm simply by using the intuitive notions of potentiality and actuality. For example, an actual masterpiece of painting has higher worth than the blank canvas and unused paint that constitute a potential masterpiece. This sort of argument can also be used to justify terraforming on worlds whose lifeforms are not (yet) people and, obviously enough, on worlds that merely have the potential of producing life.

While the analogy between the two has merit, there are obvious ways to try to break the comparison. One obvious point is that in the case of abortion, the woman is the “owner” of the body where the aborted entity used to live. It is this relation that is often used to morally warrant abortion and to provide a moral distinction between a woman choosing to have an abortion and someone else who kills the product of conception (again, I’m using neutral terms to avoid begging the question).

When humans arrive to terraform a world that already has life, the life that lives there already “owns” the world and hence humans cannot claim that special relation that would justify choosing to kill. Instead, the situation would be more like killing the life within another person and this would presumably change the ethics of the situation.

Another important difference is that while abortion (typically) kills just one entity, terraforming would (typically) wipe out entire species. As such, terraforming of this sort would be analogous to aborting all pregnancies and exterminating humans—as opposed to the termination of some pregnancies. This moral concern is, obviously enough, the same as the concern about human caused extinction here on earth. While people are concerned about the death of individual entities, there is the view that the extermination of a species is something morally worse than the death of all the individuals (that is, the wrong of extinction is not merely a sum of the wrong of all the individual deaths.

These considerations show that the analogy does have obvious problems. That said, there still seems to be a core moral concern that connects abortion and terminal terraforming: what (if anything) morally justifies killing on the grounds of (alleged) superior moral status?