Opponents of abortion (those who oppose a woman’s right to abortion and those think it is merely immoral) typically make five kinds of logical errors:

1: The seen and the unseen:

Abortion opponents see the fetus which was aborted but ignore the good things that the abortion made possible. These include the mother who is free to pursue her life goals and the lives of the children who are born into families that want and are ready for them. The decision to have an abortion is not arbitrary: it’s a choice the mother makes because she believes that she and her future children will have a better life by delaying childbirth. Extensive research confirms that abortion improves the lives of mothers and their future children. More importantly, no one, and certainly no politician is more qualified or morally justified to decide what will lead to a better life for a mother and her family.

A world without abortions is not a world with more children — it is a place with children born to parents who are not psychologically and financially ready for a life-long responsibility. Children who are born to loving parents who welcome them to the world and are prepared to care for them are far more likely to grow up into successful, mature adults. This is why protecting the right to abortion is one of the most effective ways of reducing abortions!

This failure of the imagination is known in economics as the Broken Window Fallacy – we see the economic activity created by the need to repair a broken window, but do not see the goods that can no longer be bought because they were redirected to fix that window. Likewise, we see the children who are products of unwanted births, but we don’t see the children who never had a chance to be born into a family that wanted them. Instead, countries that ban abortion deal with higher rates of single-parent families, poverty, and crime.

2: Genetic determinism:

Abortion opponents equate a human being with his genetic legacy. To them, an aborted fetus represents a lost potential life, with all its richness. But the inherent value of a human life is not determined by our genes, but the interaction of our genes with the environment we grow up in, especially the ideas and culture we are exposed to. A fetus is only a part of the recipe for a human being. A human being is not merely a biological machine, but a rational animal, with a rich internal life. We can argue when that mental existence becomes a possibility, but it is certainly closer to birth than conception.

To take a sci-fi scenario, a fetus grown into a brain-dead grown adult in a vat is not a full human being either. Human beings are the synthesis of biology and culture. Theists often talk of the fetus as having a “soul”, but whether you believe in genes or a mystical essence, the error is the same.

3: Potential vs actual:

A fetus is a potential human being, not an actual one. The ingredients for a cake on a table cannot be called a cake. A seedling is not a tree. A fetus is a potential human being and only becomes one under specific biological conditions.

The distinction is especially clear early in the pregnancy: a blastocyst is a microscopic clump of cells, physically almost identical to the fetus of any other mammal. To say that a bit of protoplasm is a human being ignores the essence of what a person is: an independently functioning rational animal.

A human being can exist without an exclusive biological dependence on a host, intentionally interact with its environment, and possess the basic attributes of cognition. A fetus lacks these attributes. True, a newborn infant is entirely dependent on others for its continued survival, but this is a relationship, not a biological necessity. Virtually everyone in a civilization would soon die without the cooperation of others, but these are contractual relationships, not biological dependencies. A baby can be adopted by a willing family, a fetus cannot.

The moment of birth presents a clear physical, biological, and psychological point when a parasite (as an analogy, not a derogatory term) becomes a metaphysically independent being.

4: Continuum fallacy:

This is the logical fallacy of denying that a distinction exists because there exists a continuum. For example, there is no clear distinction between a stubble and a beard, yet the existence of unclear cases does not invalidate our ability to identify someone with a beard. Likewise, difficulty in identifying the exact instant that a fetus becomes a human being does not mean that there are no clear differences between a fetus (say, a single-celled ovum just after fertilization) and a clear example of a human being (an infant, or you and me).

We can acknowledge difficulty, and err on the safe side for moral or legal reasons, but we need to base our conclusions on facts, not arbitrary religious doctrine. I outlined what I believe are the relevant facts in the “potential vs actual” section above. By contrast, I think that the act of conception meets no reasonable criteria, especially at the beginning of the pregnancy. As I detailed, a fertilized ovum is not metaphysically equivalent to a human being, and only begins to approach that status towards the moment of birth, which firms an unambiguous epistemological and therefore legal distinction. (We can argue about the ethics of late-term abortion, but they are a red-herring in the debate the meaning of conception.)

5: False dichotomy between moral absolutism and subjectivism

A false dichotomy is a false alternative between an either/or situation when an additional position exists. In regard to abortion, the dichotomy is this:
“Women must be responsible for their sexual choices and forced to bear children they do not want in order to preserve traditional marriages, families, morality, religion, or another value. Either we hold people responsible for their choices or anything goes.”

There are two false dichotomies in regard to abortion:

First, there is no fundamental conflict between women leading moral lives, raising families, and observing religious beliefs and the practice of abortion. There is no inherent conflict between these concepts. Of course, some religious groups claim that abortion goes against their tenets, but there is no fundamental conflict between these practices, and indeed many religious groups allow for abortion with no ill effect to their basic tenets. More importantly, there is no fundamental conflict between living a virtuous life and abortion, whether individually or as a society. In Western countries such as Germany, France, and Australia, abortions are widely practiced and accepted, and yet are completely incidental to their moral qualities.

Second, there is no conflict between a lifestyle which separates sexuality from parenthood and healthy, loving, responsible families. Modern society has provided men and women with safe and effective technologies that separate sex and childbirth — condoms, birth control pills, emergency contraception, and as a last resort, abortion. These tools liberate women by allowing them to enjoy fulfilling sexual lives for the first time in human history.

While independent women with sexual agency are a threat to those who wish to force them into their vision of a woman’s role in society, there is no reason that women who desire sex for reasons other than childbirth are incapable of healthy and responsible relationships, marriage, and child-rearing.  Having sex for pleasure without the risk of a lifelong obligation does not preclude women and men from forming healthy romantic relationships.  Even abortion critics must accept this – or require a fertility test before any couple is allowed to have sex or marry.  What about those who are infertile or past menopause?

Allowing women to choose when they are ready to raise a child greatly improves the likelihood of raising children in stable, loving families. Children should not be a sacrificial obligation which women must be forced into, but a personal, selfish choice that parents pursue because it will bring joy and a multitude of other benefits into their lives.