Embryology textbooks and honest defenders of abortion like the philosopher and ethicist Peter Singer agree: it is an objective scientific fact that a fetus is a member of the species Homo sapiens. Morality only enters the issue once the scientific facts are on the table. However, most defenders of abortion are loathe to admit that they favor a system of morality that separates human beings into those that have a right to life and those that can be legally killed. Thus, abortion defenders consistently confuse the scientific issue of being a human with the moral issue of being a person.
Scientific Consensus
You are not committing the logical fallacy of appeal to authority when you appeal to legitimate authorities. This may not mean that you are right, but it is a legitimate form of evidence, so that is where we will start: with scientific consensus. There are several lines of evidence for this. The most important is that it is accepted scientific knowledge that a fetus is a distinctly new member of the species. Embryology textbooks recognize this. Many biologists are pro-choice, but because they grant less ethical weight to a fetus, not because they do not believe it is a human.
Here is an assortment of embryology textbooks that support this point:
- William Larson, Human Embryology, 3rd edition, page 1
- Keith Moore and T.V.N. Persaud, The Developing Human, 6th edition, page 18
- Ronan O’Rahilly and Fabiola Mueller, Human Embryology and Teratology, 3rd edition, page 8
- Scott F. Gilbert, Developmental Biology, 6th edition, page 185.
Honest defenders of abortion will also admit this. For example, see page 86 of Practical Ethics the utilitarian ethicst Peter Singer. He freely admits that a fetus is a member of the species Homo sapiens, but defends abortion on the grounds that granting Homo sapiens a special moral status is speciesist. And in the article When does life begin? An embryologist looks at the abortion debate, the embryologist Clifford Grobstein freely admits this as well (both Grobstein and Singer take the position that merely being a human is not sufficient to grant rights; this is defensible, but it does require the rejection of the doctrine of unalienable rights for all human beings).
Definition of Life
We do not have to accept the scientific consensus. Instead we can follow along with the evidence itself. Scientists have yet to create a fully satisfactory definition of life, which is why debate rages about the status of viruses. But luckily fetuses are not as difficult to classify. The famous mathematician John Von Neumann created the most elegent definition of life, here is a simplification. A living thing is anything with (1) an internal blueprint of itself (such as DNA), and (2) an intrinsic capacity to use that blueprint in self-creation.
Consider how some common objections raised by abortion defenders fail this test:
- Sperm and eggs do not have a complete internal blueprint because they only have half the necessary chromosomes.
- Toenail clippings and kidneys have the DNA, but lack the capacity to use the blueprint - most of the genes are switched off unavailable for use (this is not the case for lower lifeforms - if a part is removed it really can fully use the DNA to make a new version of the organism).
- Cloning machines applied to human genetic materials also fail the test because the building capacity is no longer intrinsic to the organism. Instead it relies on the external machine. An abortion defender might change the point of reference and claim that the combination of the cloning machine and the genetic materials are one organism. But that still fails because there is no blueprint (DNA) for the combination of human and machine.
But a fetus passes both tests. It has the DNA, and it has the capacity to fully utilize that DNA in self-creation. It is a unique organism.