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- John Burgess (2010). Could a Zygote Be a Human Being? Bioethics 24 (2):61-70.This paper re-examines the question of whether quirks of early human foetal development tell against the view (conceptionism) that we are human beings at conception. A zygote is capable of splitting to give rise to identical twins. Since the zygote cannot be identical with either human being it will become, it cannot already be a human being. Parallel concerns can be raised about chimeras in which two embryos fuse. I argue first that there are just two ways of dealing with cases of fission and fusion and both seem to be available to the conceptionist. One is the Replacement View according to which objects cease to exist when they fission or fuse. The other is the Multiple Occupancy View – both twins may be present already in the zygote and both persist in a chimera. So, is the conceptionist position tenable after all? I argue that it is not. A zygote gives rise not only to a human being but also to a placenta – it cannot already be both a human being and a placenta. Neither approach to fission and fusion can help the conceptionist with this problem. But worse is in store. Both fission and fusion can occur before and after the development of the inner cell mass of the blastocyst – the entity which becomes the embryo proper. The idea that we become human beings with the arrival of the inner cell mass leads to bizarre results however we choose to accommodate fission and fusion.
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When does a human being begin to exist? Barry Smith and Berit Brogaard have argued that it is possible, through a combination of biological fact and philosophical analysis, to provide a definitive answer to this question. In their view, a human individual begins to exist at gastrulation, i. e. at about sixteen days after fertilization. In this paper we argue that even granting Smith and Brogaard's ontological commitments and biological assumptions, the existence of a human being can be shown to begin much earlier, viz., with fertilization. Their interpretative claim that a zygote divides immediately into two substances and therefore ceases to exist is highly implausible by their own standards, and their factual claim that there is no communication between the blastomeres has to be abandoned in light of recent embryological research.
Is the human zygote and human embryo a human being? Such questions are biological questions (although philosophy may helpfully be drawn upon in rebutting objections and clarifying concepts). The issue of personhood is thus best kept entirely off the table when that question is being discussed. What is, or is not, possible for ontological persons, and what would, or would not, be morallywarranted for moral persons, should not play a role in the assessment of biological evidence with a view to answering the biological question. Yet this is what happens in a recent essay by Bernard Prusak (ACPQ 82:3 [Summer 2008]), an essay devoted to showing why the “problem of the embryo” will always be with us. More careful attention to developmental biology, and greater care in distinguishing scientific from metaphysical and ethical questions, would go some way towards making the problem of the embryo less intractable than Prusak believes.
No categories
Alfred Mele’s zygote argument for incompatibilism is based on a case involving an agent in a deterministic world whose entire life is planned by someone else. Mele’s contention is that Ernie (the agent) is unfree and that normal determined agents are relevantly similar to him with regards to free will. In this paper, I examine four different ways of understanding this argument and then criticize each interpretation. I then extend my criticism to manipulation arguments in general. I conclude that the zygote argument is no threat to compatibilism.
ABSTRACT: The rare condition known as dicephalus occurs when (prior to implantation) a zygote fails to divide completely, resulting in twins who are conjoined below the neck. Human dicephalic twins look like a two-headed person, with each brain supporting a distinct mental life. Jeff McMahan has recently argued that, because they instance two of us but only one animal, dicephalic twins provide a counter-example to the animalist’s claim that each of us is identical with a human animal. To the contrary, I argue that in cases of dicephalus it is obvious neither that there is one animal nor that there are two of us. Consequently, the animalist criterion does not straightforwardly apply to cases of dicephalus. I defend an account of dicephalus that is both sensitive to the complexity of twinning phenomena and not inconsistent with animalism. On my view, dicephalic twins are a borderline case of the concept human animal. I conclude with some speculative remarks about the normative import (if any) of my claim that dicephalic twins are a borderline case.
The rare condition known as dicephalus occurs when (prior to implantation) a zygote fails to divide completely, resulting in twins who are conjoined below the neck. Human dicephalic twins look like a two-headed person, with each brain supporting a distinct mental life. Jeff McMahan has recently argued that, because they instance two of us but only one animal, dicephalic twins provide a counterexample to the animalist's claim that each of us is identical with a human animal. To the contrary, I argue that in cases of dicephalus it is obvious neither that there is one animal nor that there are two of us. Consequently, the animalist criterion does not straightforwardly apply to cases of dicephalus. I defend an account of dicephalus that is both sensitive to the complexity of twinning phenomena and not inconsistent with animalism. In my view, dicephalic twins are a borderline case of the concept HUMAN ANIMAL. I conclude with some speculative remarks concerning the normative import (if any) of my claim that dicephalic twins are a borderline case.
That the soul of a human person is infused at conception is a metaphysical claim. But given its traditional articulation, it has the empirical consequence that the zygote must have a substantial continuity with the adult person, a continuity which is already determined at conception. This empirical consequence is contradicted by the fact that the zygote may become a hydatidiform mole, or several persons. The metaphysical claim is falsified by the facts. Keywords: abortion, information capacity, metaphysical account, person, zygote CiteULike Connotea Del.icio.us What's this?
It is no longer possible to claim that the biological characteristics of the future adult are already determined at conception. After all, a zygote may develop into a hydatidiform mole rather than into a human being. The development of an individual human person is determined by genetically and nongenetically coded molecules within the embryo, together with the influence of the maternal environment. Consequently, it is an error to regard the zygote's chromosomal (and other) DNA as sufficient to determine the uniqueness of the future individual. Keywords: information capacity, molecular biology, personhood, zygote CiteULike Connotea Del.icio.us What's this?
In this paper I defend the view that a zygote is a human from the fission objection that is widely thought to be decisive against the view. I do so, drawing upon a recent discussion of this issue by John Burgess, by explaining in detail the metaphysical position the proponent of the view should adopt in order to rebut the objection.
Discussion of John Burgess, Could a zygote be a human being?
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