Natural Law Abortion? Another Response to Gunther Laird

Gunther Laird in his book The Unnecessary Science: A Critique of Natural Law Theory offers a number of arguments against Edward Feser’s account of natural law. Laird claims that on a number of issues, including abortion, Feser’s natural law theory fails to actually support Feser’s own position on abortion and can in fact be used to support abortion. I have written against Laird’s argument on same sex marriage here. Below, I will address his argument regarding abortion.

Laird’s Argument

Laird makes two important claims in his argument that abortion is defensible on natural law grounds. First, he claims that if appeal to a human zygote’s potencies is sufficient to make it a human person, then a human egg or sperm is likewise a person. Second, he claims that the moment of birth gives to a fetus an intrinsic principle which makes it an independent living being. Let us look at each in turn.

Zygote = Egg = Sperm?

Laird espouses some skepticism that a single celled human zygote is metaphysically the same thing as an adult human. He writes:

A zygote has a vastly different structure and organization patern from a fully-grown human being…By Feser’s own definition it seems obvious that an adult human being instantiates a different Form, which would mean that zygotes might not actually be human and thus fair game [to kill] (emphasis his).

The Unnecessary Science pgs. 149-150

Laird then acknowledges that Feser would note that while a zygote does not in actuality have many of the properties of an adult human e.g. the ability to reason, it does have them potentially and is directed towards such an ability. Here Laird thinks there is an issue for, he claims, if a zygote is a human because it is directed towards becoming an adult, doesn’t that mean sperm and eggs are human beings too?

Feser himself would say that the only reason eggs exist is to create new human beings…That means the egg’s final cause is to become a human being which also means it is ‘directed towards’ human rational activity…The only thing the little egg needs to realize that potential is a little help from a little sperm followed by nine months in mommy’s tummy. What makes the egg’s situation metaphysically different from the zygote’s? (emphasis his)

The Unnecessary Science 150-151

The obvious answer to Laird’s question here is that an egg or sperm cell is biologically a completely different kind of thing from a zygote which is its own biological organism. An egg or sperm is a sex sell of some organism whereas a zygote is itself an organism with its own intrinsic principle of growth. They are quite obviously different kinds of things and this can be shown as follows.

Laird’s claim that both a zygote and egg share the same end is false. The end of a sperm is to fertilize an egg, that of an egg to become fertilized by a sperm and that of a zygote is to develop into a more mature human form. That these three ends are different already tells us that egg, sperm, and zygote are (as is obvious) three different kinds of things rather than all being a human being. Things with distinct ends are distinct kinds of things. When fertilization is accomplished, both egg and sperm cease to exist as egg and sperm and a new kind of thing comes into being, namely a zygote which is a new human organism. The fact that the egg and sperm cease to exist is important. It is not true to say that a sperm develops into a zygote and then to a fetus and then to a teenage and so on. The sperm exists to fertilize an egg. Once this has been done, the sperm has reached its end and a substantial change has occurred resulting in the existence of a new substance which is neither a sperm nor an egg. This new substance has its own intrinsic principle of growth and will grow if in its proper environment to become a more mature human being.

Intrinsic Principles

However, Laird doesn’t like this answer. He claims that it is false to say that a zygote has its own intrinsic principle of growth and thus it is in the same metaphysical category as a sperm or egg.

A zygote is not really like an adult cat or dog or squirrel or other animal Feser uses as examples of natural substances. A grown independent animal is capable of taking in nutrients, reproducing, and carrying out all its other behaviors…on its own volition and does not necessarily rely on any other entity to do it for them. In other words, these animals operate entirely according to their intrinsic principles…A zygote, on the other hand, relies entirely on its mother’s body to carry out its distinctive operations.

The Unnecessary Science 155

Laird clearly does not understand what an “intrinsic principle” is and seems to think it has something to do with volition. The fact that some animals have their own volition and can hunt or forage for example does nothing to distinguish them from other living things qua living things. Does he think that on the Aristotelian view that bacteria, grass, and jellyfish are not truly natural substances because they lack volition? It is of course true that a zygote or a fetus takes in nutrients from its mother’s body just as a plant does but that does nothing refute the fact that each operates by an intrinsic principle. It is precisely because they function in accord with such a principle that these organisms take in nutrients as they grow and develop.

Laird however continues his argument and tries to show that the view he is offering as genuinely Aristotelian is consistent with a rejection of infanticide. he claims that though unborn humans lack an intrinsic principle of growth, born humans have such a principle as is evidenced by their crying.

We have established that zygotes do not posses this principle because their growth and development is dictated entirely by an external actor…However, when a baby leaves the womb, loses the umbilical cord, and takes the first breath out in the world, he or she gains that intrinsic principle…Even though babies are helpless, they are not as helpless as a zygote, embryo, or fetus. Babies are capable of manifesting behaviors all on their own and exerting some control over their environment even if only in a very thin sense of crying loudly to get someone to notice them. (emphases his).

The Unnecessary Science 158

This is a rather bizarre claim. Somehow, by mere locomotion and the cutting of a cord connecting a baby and its mother–both extrinsic changes to the child–the child somehow gains an intrinsic principle of growth. Laird of course does not explain how these extrinsic changes magically generate within the child an intrinsic principle of growth except by saying that the babies now exert some control over their environment by being able to cry. Again it seems that the baby’s ability to affect other peoples volition is somehow key. Laird should perhaps notify mothers everywhere that before birth, their unborn baby exerted no control over its environment. Evidently the mothers’ large bellies, their pain caused by their child’s various positions, their change in appetite, smell, and a hundred other changes were purely the result of their own volition. After all, their babies had no control over their environment!


So much for Laird’s arguments about abortion. By both conflating three clearly distinct entities: sperm, egg, and zygote and by failing to understand what an intrinsic principle of growth is, Laird’s argument that abortion is consistent with natural law is a failure. Laird makes further arguments about infanticide which I will perhaps respond to at a later point.

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