Re: Logical Fallacy of Assumption?
SCoates wrote:Thesis: Abortion is unethical as soon as the fetus shows brain activity.
Support: (In our state) euthanasia is illegal when the body shows brain activity.
Therefore, it is wrong to abort a fetus with brain activity.
I'm having trouble convincing my students that the argument is unacceptable. It is difficult for me to word why. I find the argument logically offensive as it presumes the audience agrees that euthanasia is unethical, and equates "illegal" with "wrong."
There are two issues here: (1) the general question -- is the argument logically sound? and (2) the specific question -- can we equate "immoral" with "illegal?" I'll take the second, easier question first.
If we can agree that it is immoral to break the law, then it is rather easy to conclude that what is illegal is also immoral. After all, to act illegally is, by definition, to act in contravention to the law, and so every illegal act is also immoral to the extent that it is immoral to break the law. Thus, if euthanasia is illegal, then committing euthanasia is also immoral. Whether euthanasia is immoral
as an act (i.e. divorced from its legal consequences) is another question entirely, but fortunately it's not one that we have to deal with in this context.
The second question is rather interesting, and I commend your students for coming up with a fairly sophisticated argument (that reflects well on the teacher, no doubt). It's not a good argument, mind you, but it's at least better than a lot of the other anti-abortion arguments that one runs across these days.
As I see it, the argument boils down to this syllogism:
(1) People and fetuses (after a certain gestational stage) both display brain activity;
(2) There is a moral rule forbidding us to kill people who display brain activity;
(3) Therefore, it should be immoral for us to kill fetuses who display brain activity.
The first proposition is, I think, non-controversial, but the second is suspect. Just because it is immoral to kill people who display brain activity, it doesn't necessarily follow that it is immoral to kill them
because they display brain activity. The argument, therefore, has to rely on an unstated proposition:
(2)(a) Brain activity is the sole criterion upon which we judge whether a thing may be killed or not.
But that obviously isn't true. All animals with brains display some sort of brain activity, but we kill animals all the time -- and not just for purposes of euthanasia. We kill animals for food, for sport, for convenience, for financial gain, and for all sorts of other reasons. So proposition (2)(a) cannot form one of the premises for conclusion (3), as it would lead us to conclude that it would be immoral for us to kill
anything that displays brain activity, and it's unlikely that any of your students would want to go that far in their argument.
To make the syllogism work, then, the unstated premise must look something like this:
(2)(b) Brain activity is the sole criterion upon which we judge whether a [i]person[/i] may be killed or not.
This premise avoids the problem of over-inclusiveness by restricting the argument solely to people. But premise (2)(b) relies upon a non-common term: "person." In order for the conclusion (3) to follow from this premise, we have to assume that "fetuses" are "persons" (to see why this is true, substitute "dogs" for "fetuses" in the syllogism). That assumption, however, is not warranted. Indeed, most people* would argue that the fetus's personhood is
the central question in the abortion debate.
Your students' argument, therefore, rests upon a classic logical fallacy: it begs the question. In simpler terms, your students are assuming that which they are required to prove.** In this case, they are assuming that fetuses are persons (and thus are subject to the same ethical principles as persons) when, in fact, they are obligated to
prove that fetuses are persons. For if fetuses are not persons, then your students' euthanasia argument doesn't make any sense.
*I'm not one of them.
** I think you had a vague sort of grasp of this point when you used the analogy of the Christian relying the bible to make an argument about the immorality of homosexuality. That would be another example of question begging.
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