|Ultrasound of twins at 6 weeks (not mine, fyi!)|
One thing seems pretty clear--it's not until 20 weeks gestation (very roughly, and at the very least) that a fetus starts to be conscious, so there are no "selves" on the scene before then. Whatever I saw on the ultrasound at 6 weeks, it wasn't a self.
Another thing seems clear--it takes some pretty advanced properties (e.g. self-awareness) to be a full-fledged person. It's doubtful that there's a person on the scene until some point after birth. So whatever I saw on the ultrasound, it was neither a self, nor a person.
That doesn't directly answer the question, though. Granted what I saw via ultrasound wasn't a self or a person, it could still have been one of my kids -- i.e. one of my kids before they became selves or persons.
One line of thinking says that makes perfectly good sense. Over time, we take on and lose lots of properties. One and the same individual will be a child over part of his lifespan, but an adult over another part. You're a non-parent for the first many years of your life, and then perhaps become a parent. You can start off not being an American citizen, and then become a citizen. At some point you may become a lawyer or a doctor or a novelist.
The fact that a property is profoundly important, making you in some sense who you are, once you have it, doesn't mean that it's literally an essential property--one that you can't exist without. Not all of our important attributes are "born again" attributes--ones that make a new entity exist, once they come on the scene. So it's not out of the question that the very same individual existed as a zygote, later becoming a self, and still later becomes a person ... an adult, a parent, a citizen, a lawyer, etc.
Another line of thinking says that once a locus of consciousness (a "self") comes on the scene, there's a new entity there that didn't exist before. Selfhood is indeed a "born again" property: when it emerges, a whole new entity emerges. Or you might say no to that, but yes to personhood being that sort of property. You might think that whenever a person comes on the scene--a locus of self-awareness--a new entity exists. The old entity--the fetus, immature infant, whatever--is replaced by a numerically different entity, a second entity.
On the second view, Sam only existed when his locus of consciousness existed (or his locus of self-awareness), so I didn't have first contact when I saw his heartbeat on the ultra-sound image. That wasn't Sam, and the other blob wasn't Becky.
The first view says the change from being a fetus to being a self or person is like metamorphosis. When a caterpillar becomes a butterfly, one entity isn't replaced by a second entity. This is just change. Butterflies might be ever so proud of being able to fly (if they could think about it), but they have to live with the fact that once they were caterpillars. Similarly, as profound as it is to be a person or self, selves and person were once upon a time zygotes.
The second views says the change from being a zygote to being a self, or from being an immature infant to being a person, is more like the moment in the fairytale when the frog become the prince. The prince is (presumably) a whole new entity, not the same entity with new properties. Only with human development, we have a better scientific understanding of how the dramatic changes takes place. The brain matures to the point that the "lights" are on, and then later the brain supports the power of self-awareness.
The first view is associated with the "animalist" account of personal identity--the view that says humans are essentially organisms. The second view is associated with the Lockean psychological continuity account of personal identity, the one that most philosophers today accept. I'm leaning toward ...
No, I won't say! More on these things later in the week.