The Derivation of Pluripotent Stem Cells:

(A) From Early Embryos, (B) From Aborted Fetuses

Totipotent: Possessing the potential to develop into an entire organism (given the right environment).

Pluripotent: Possessing the potential to give rise to most (but not all) tissues of an organism.

Multipotent: Possessing the potential to give rise to a certain particular family of cells (e.g. blood cells).

Primordial Germ Cells: In the above case, fetal cells from which the testes or ovaries would develop.

  

Another Method:

Somatic Cell Nuclear Transfer ("Cloning")

Here, we start with an egg from which the nucleus has been removed, and an ordinary somatic cell from an adult (e.g. a skin cell), and fuse them. In principle, this can result in a totipotent cell comparable to a fertilized egg, which could develop in the same way as in the previous diagram. If implanted and allowed to develop all the way, it would result in a human being who is a clone of the donor of the somatic cell. If developed only to the blastocyst stage, however, it could be used as a source for pluripotent stem cells.

(Illustrations courtesy of NIH: www.nih.gov/news/stemcell/primer.htm)

 

Ethical Question: What kind of moral status, if any, does a blastocyst possess? In other words, what kind of moral consideration does it merit? Specifically, is the moral standing of an embryo--a blastocyst, at this stage--perhaps significant enough that we should refrain from harming it, even for good ends like deriving stem cells for medical treatment and research? Or is an embryo's moral standing limited enough that even though it counts for something, its importance is outweighed by the benefits of stem cell research, so that the ends justify the means?

One possibility: the blastocyst is a person, with a full human right to life, just like us, so that it is just as important an entity as you are. IF that's correct, then that obviously would present a grave moral problem for any kind of medical research or treatment that involves deriving stem cells from blastocysts, which destroys them.

(A) What are some arguments for that position, and are they convincing?

(1) The argument from humanity:

(i) All human beings have a full right to life.

(ii) Embryos are human beings.

(iii) Therefore, embryos have a full right to life.

Is this argument logically valid? Is it sound? What are the problems with this argument?

(2) The argument from potentiality:

(i) A blastocyst is a potential human being.

(ii) Human beings have a right to life.

(iii) If an X has a right, then a potential X likewise has that right.

(iv) Therefore, a blastocyst has a right to life.

Is this argument logically valid? Is it sound? What are the problems with this argument?

(3) The argument from continuity, and the arbitrariness of drawing sharp lines after conception:

(i) The embryo is the earliest stage in a continuous process whereby a single entity develops into a human being.

(ii) But there's no place along that continuum of development to draw a sharp and non-arbitrary line and say: this is where it goes from being a non-person to being a person.

(iii) The only safe thing to do in this sort of continuum situation is to refuse to draw any such line, and instead treat all the different stages equivalently.

(iv) Thus, the only safe thing to do is to regard an embryo as the moral equivalent of an ordinary human being, possessing the same moral standing.

Is premise iii true? I will discuss some reasons for thinking that it is not, and articulate at least one alternative approach to such continuum situations (with interesting parallels concerning other issues, such as how to understand the value or moral status of non-human animals). Often people seem to accept premise iii simply because there seems to be no alternative, so it is important to be aware of other conceptual alternatives, such as the Gradualist View I'll discuss, so that the pro's and con's of each approach can be explicitly compared. Be sure you understand the complex issues here. We will return to some of these issues when discussing other topics.

(B) Two Arguments against the idea that a blastocyst is a moral person (to be described in lecture, if we get to it):