A human foetus at 11 weeks.
I want to know whether that thing inside my mother’s womb, which weighed around 7 grams and had gill slits, was me. We acknowledge that it was a potential person; but can we acknowledge that it was the same person?
In line with the ‘Biological View’, it was because I am one continued organism: that is, I exhibit the same genetic coding and biological arrangement of cells as the foetus did. But there are unintuitive consequences to defining a person like this. If a surgeon removed significant components of my brain now, for example, the organism left behind would still be me apparently. This doesn’t seem exactly right.
According to the ‘Standard View’, I was never a foetus—or even a six-month-old baby—because the foetus did not have the mental capacities I have now (memory, personality, and so forth). But while this view is appealing at first, there’s an obstacle in the ‘Too-Many-Thinkers’ problem: if I emerged as a person from a foetus, what happened to the foetus?!
Option 1: The foetus was a person, too, but it existed in some vegetative state: I effectively destroyed it when I emerged as the person I am now. But then how did I make this entity perish with my mental capacities?
Option 2: The foetus survived and there are two people sharing one physical space (my body). But then there are too many ‘thinkers’ in one body and I am not sure which one I am!
The question of whether I was a foetus is an interesting question and there are no clear answers.
No one who respects modern embryology is seriously denying that I was engendered in some way by my prior body. Indeed, I wouldn’t be alive today were it not for that foetus. However, as Olson says, these are biological facts. Moreover, when did these biological facts become relevant to my beginnings? Do they accompany the facts surrounding my conception and facts stretching back to the ‘Big Bang’—of the astronomical kind, not of the sexual kind relating to my parents! Either way, no facts about my physical and biological beginnings tell us whether I am metaphysically at one with that thing.