Are the unborn "individuals"?

As is my occasional wont, I got into it again today with the usual crowd of pro-choice folks tweeting their bumper-sticker slogans on Twitter. Today, the argument was that the unborn are not "individuals," by virtue of the fact that they depend on the body of another human being to survive.

You'll note that this is a functionalist definition of the term. Functionalism defines a person (or a human being or individual, as the case may be) by their function or behaviour: in other words, how human you are depends on what you can do, not on who or what you are.

Contrast that with the primary definition of "individual" as given at Dictionary.com: "A single human being, as distinguished from a group." A fetus certainly does meet this definition: a DNA test would rule out her being one of her mother's body parts, for example.

Aha, my Twitter opponent countered, but what about twins, then? Identical twins have identical DNA. Was I arguing that they are not individuals?

First of all, this missed my point, which was that they are individuals with respect to their mother. Fetuses are not body parts. What they are in relation to each other, on the other hand, is beside the point. (And even the fact of identical DNA is not so cut and dried.)

But nonetheless, I decided to press this question just a little farther. What do you do with conjoined twins? Take, for example, the Hensel twins, who share several vital organs. Abigail and Brittany Hensel were not separated at birth because of the unlikelihood of one twin surviving. They are highly coordinated and have learned to walk, swim, drive a car, and even type, even though each twin controls one arm and one leg. They are absolutely dependent upon one another for survival.

Are they individuals, I asked? Repeatedly. I got a lot of filibustering and personal abuse. What I did not get, however, was an answer.

Despite the necessity of the Hensel twins' functioning together, they are individuals. They have different likes and dislikes. They have different tastes in clothing, such that their joined garments are specially tailored to express their individuality. They each had to earn their own driver's licenses. So despite their dependency on each other's bodies for survival, they are indisputably individuals. And that is according to a functionalist definition.

How human you are does not depend on how dependent you are on another human being. Abigail and Brittany Hensel are not each half-human or half-individual because they could not survive separately. And neither are the unborn because they cannot survive outside the womb. The facts of life simply do not square with glib pro-choice rhetoric.