In response to the last question, “Why can we kill unborn children?” Whether or not a fetus is a person and therefore due the same level of moral consideration as us, the rights of one person cannot infringe on the rights of another. No one may force me through nine months of great physical stress, steal my vital nutrients and finish with a major medical procedure just so that they may be able to live. So, the issue is whether abortions should be legal. Yes, they should.

But then, what makes a person a person? I do think this second question is just as important, and certainly more interesting. However, I find the acronym, SLED (size, level of development, environment and dependency), as laid out by Parker Trelka, entirely inadequate.

It fails to answer why we deserve moral consideration and what deserves the same level of moral consideration as us? The understanding of SLED laid out certainly suggests that a fetus’ differences are not enough to deny it our level of moral consideration. But why does the fetus deserve it? If we look at Trelka’s understanding of SLED, my goldfish appears to be as human as any fetus. But surely it is not a person. Let’s look at each aspect of SLED, so that at least we can say my goldfish is not a person.

For Size, it appears a comparison between height and weight of two grown adults is out of place here. Wouldn’t it be more reasonable to compare a person’s organs to the size needed to perform their roles? My lungs and liver are the right size for me. They are no longer growing, and there is no reason to compare them to anyone but me. However, this could still suggest the humanity of my goldfish, as its organs seem appropriately sized. 

For level of development, we should not disregard the fact that a person’s level of development does matter. We do not treat children as fully human. We deny them plenty of rights and don’t think twice. We recognize their lack of critical thinking and hold adults more accountable. IQ may be of little value, but notions of object permanence are vital to our lives. Recognizing this has the added effect of excluding my goldfish from personhood.

Environment gives me two major troubles. The first concerns the fetus’ environment’s level of dependency on the mother, but I will save that for dependency. The second is that a person’s environment does have a major impact on who they are. A person’s environment affects how they live, what they eat and the things they experience. I disagree with environment as a criterion for personhood, but a person confined to a womb lives the life of the mother, not of a separate individual.

Finally, dependency. It is true, humans are social creatures and depend on one another for a long list of things. But none of those things can be forced upon the mother to the degree a fetus requires. A diabetic’s dependency doesn’t require nine months of constant care from a dedicated nurturer (much of it spent with back pains while throwing up) that ends in a life-threatening and painful medical procedure. The fetus’ dependency does. 

When we understand SLED in this way, it does appear as though a fetus is not a human. However, SLED fails to capture the complexity of what it means to be human anyways. There is no concern for the complexity of our experience, our choices or our knowledge.

Personally, I prefer to use the five considerations Mary Anne Warren lays out in “On the Moral and Legal Status of Abortion”: Consciousness, reasoning, self-motivated activity, the capacity to communicate and the presence of self-concepts. This understanding still suggests a fetus is not a person. However, as I said at the beginning, whatever understanding of personhood we use, no person is granted the moral privilege needed to justify criminalizing abortions.