The side panel of this article (which is essentially an abstract with alink to the audio) at "NPR : U.S. Scientist Questions Korean Stem-Cell Research," raises the essential question about the ethics of embryonic stem-cell research this way:
For many, the decision to proceed with stem cell research ultimately rests on whether a human embryo is a human.
This is such a muddle-headed way of posing the question. A trivial answer, "Of course it's human. What else could it be?" doesn't begin to get at the meat of the disagreement. The question should be posed this way:
What value is inherent in a human being in even the earliest stages of development that would morally preclude us from treating such a person as a means to an end?
It might help us to focus on this form of the question, because it will help us to appreciate how crucial the question of the value of any human person is. When we adopt a materialistic perspective as our starting point, every value collapses (taking the consequences of this line of thought far enough). When we recognize that it is only the human soul that accounts for free will, and which ultimately raises all human beings, at any stage of consciousness, to a level beyond all value derivative from practical considerations, we can come to appreciate the real crisis of understanding and value in our culture.
For example, suppose we were to assume that the observable and measurable universe of space-time is all the reality there is -- a pretty reasonable assumption for most scientists. (Even many scientists of the Christian faith have a notion that free will can somehow be shown to be an emergent property of biological organisms of sufficient complexity. Any decent physicist could show that this idea is simply mistaken, and demonstrates insufficient grasp of mathematics.) We would be forced to conclude that all value is inherently material in nature. We would conclude (not from any absolute principle, but from general agreeableness) with the utilitarians that consciousness, in its highest forms, is the source of value. Then, knowing (we suppose) that all consciousness is an emergent property of biological systems, we would realize that, in principle, human beings could ultimately design a system with an artificial intelligence (and an artificial consciousness) to have greater inherent value than any human being. (Douglas Adams, in his Hitchhiker's Guide to the Galaxy referred to such an invention as "Deep Thought." What would SNL's Jack Handey have said about all that?)
At that point, humanity would have outlived its usefulness and would "Go gently into that good night." This, of course, would free human beings of the burden of sticking around until the universe dies a heat death from progressively increasing entropy.
If all of the above is recognized as being the absurd rantings of a materialist philosopher, we can begin to appreciate the need for hypotheses that go beyond the material. If not, then we will be stuck in our own primordial juices, subject to the moral and spiritual equivalent of the second law of thermodynamics, for a very long time.