Is your answer any different for identical twins, who of course only separate after fertilization? How about chimeras?
Yes; if I had a twin, my obvious answer would be when I separated from my brother. Were I a chimera, I suspect I would have researched the issue more extensively than I have now, but at my present level of understanding it still seems like there’s a discontinuous event- when the cells fuse together to form one organism.
It seems to me that you can find a discontinuous event for most person precursors, and the discontinuity is important for that question (because the components were continuous beforehand, and the composite is continuous afterwards). The main counterexample I can think of is clones- if I create a thousand copies of my DNA and implant them in embryos scrubbed of DNA, then they seem fungible in a way that a thousand unique fertilized embryos are not. And then, because they are fungible, I would ascribe to the group of them the specialness of a single fertilized embryo, and would only have qualms about destroying the last one (or perhaps last few). Note that as soon as they begin to develop, they begin to lose their fungibility (and we could even quantify that level of fungibility/uniqueness), and could eventually become unique people (that share the same genes).
Likewise, the position “every sperm is sacred” seems mistaken because sperm are by nature fungible (and beyond that, we can complain about the word sacred).
Likewise, the position “every sperm is sacred” seems mistaken because sperm are by nature fungible (and beyond that, we can complain about the word sacred).
In what way are sperm fungible? There is usually a wide variety of difference between two random ones from the same person. After all, half the genetic variability of two siblings is due to the difference in sperm.
It’s true that differences are such that we can’t easily tell much difference between any two sperm (of the same sex and chromosome number) -- but the same is true of a just fertilized zygote or just divided embryo, which you appear to count as non-fungible when you say that “I can’t think of a situation where I would be willing to accept the death/murder of a fetus or infant where I wouldn’t be willing to accept the death/murder of an adult.”
It seems that “fungibility” needs to be treated as a continuum. I think that just about all reasonable criteria for deciding this turn out on closer inspection to be fairly continuous.
It seems that “fungibility” needs to be treated as a continuum.
Agreed.
In what way are sperm fungible?
It mostly seems that way because they’re massively overproduced, but you are right to question that.
I think I’m going to turn to my claim about future development as important in identifying sperm as more fungible and fertilized eggs and beyond as less fungible, but I agree that claim is weaker than I thought it was when I made it.
Yes; if I had a twin, my obvious answer would be when I separated from my brother. Were I a chimera, I suspect I would have researched the issue more extensively than I have now, but at my present level of understanding it still seems like there’s a discontinuous event- when the cells fuse together to form one organism.
It seems to me that you can find a discontinuous event for most person precursors, and the discontinuity is important for that question (because the components were continuous beforehand, and the composite is continuous afterwards). The main counterexample I can think of is clones- if I create a thousand copies of my DNA and implant them in embryos scrubbed of DNA, then they seem fungible in a way that a thousand unique fertilized embryos are not. And then, because they are fungible, I would ascribe to the group of them the specialness of a single fertilized embryo, and would only have qualms about destroying the last one (or perhaps last few). Note that as soon as they begin to develop, they begin to lose their fungibility (and we could even quantify that level of fungibility/uniqueness), and could eventually become unique people (that share the same genes).
Likewise, the position “every sperm is sacred” seems mistaken because sperm are by nature fungible (and beyond that, we can complain about the word sacred).
In what way are sperm fungible? There is usually a wide variety of difference between two random ones from the same person. After all, half the genetic variability of two siblings is due to the difference in sperm.
It’s true that differences are such that we can’t easily tell much difference between any two sperm (of the same sex and chromosome number) -- but the same is true of a just fertilized zygote or just divided embryo, which you appear to count as non-fungible when you say that “I can’t think of a situation where I would be willing to accept the death/murder of a fetus or infant where I wouldn’t be willing to accept the death/murder of an adult.”
It seems that “fungibility” needs to be treated as a continuum. I think that just about all reasonable criteria for deciding this turn out on closer inspection to be fairly continuous.
Agreed.
It mostly seems that way because they’re massively overproduced, but you are right to question that.
I think I’m going to turn to my claim about future development as important in identifying sperm as more fungible and fertilized eggs and beyond as less fungible, but I agree that claim is weaker than I thought it was when I made it.