A philosophical preamble
Much of this unit has to do with prenatal development. This is a topic that could be discussed from a purely technical, biological, mechanistic perspective... but because it describes the way in which we all ended up getting born, it's obviously much more than that. As a result, I need to begin at an unusual place in this lecture: by talking about the fact-value distinction and how that plays out in contemporary debates about the role, nature, and limits of science.
When we think of facts, we think of something observable, and often (not always) something that can be determined objectively, even scientifically (since science is a form of systematic formal observation). Of course, there are many facts that can't be determined in that way, the most obvious being historical facts. This is because these matters, even though in the realm of the observable, are outside of the universe of discourse of the scientific method (largely because they are not replicable).
When we think of values, we think of something that is no less real and no less important, but that is by definition unobservable. As a result (at least in my view), science qua science can't provide us with values. Wherever else we may derive values from (religion, philosophy, social or political consensus, or the unexamined Zeitgeist), we can't derive them from science as such... at least, that's my view. (Some scientists, in fairness, disagree with me about that.) But that doesn't mean that values are "subjective" or that they are purely of human origin. (That question represents a major philosophical fault line in our culture: many, including myself, believe in the existence of genuinely transcendent moral absolutes, while many others do not. Since there are sensitive, tolerant, thinking persons in both camps, respect for both points of view and a refusal to "demonize" whichever side you do not belong to is, in my view, essential... unless watching the fabric of society tear apart is your hobby.)
In the realm of facts, scientists are allowed -- in fact, expected and paid -- to be defined experts. But in the realm of values, no human being is any more of a defined expert than anyone else: there's nothing about the scientific role (or the teaching role) that gives the values of the scientist (or teacher) any particular significance or validity above and beyond the values of those in other social roles. That means that, as soon as the discussion moves from facts to values, scientists (or other socially designated experts about matters of fact) have to set aside their mantle of expertise and dialogue at a horizontal level (a discussion between equals), not a horizontal or top-down one.
In talking about prenatal development, we come up against some philosophical issues that have split our culture in half for the past 30 years or more: namely, the question of what defines a person, who is a human being, and what implications our answer to that might have for the wider society (including public policy). In all probability, this semester's population of students (that's you!) is split down the middle on these issues as well. The core issues include the following questions:
My own view (which I don't ask you to share, but which I offer as a matter of intellectual honesty -- fair-minded people make their own biases and presuppositions and values explicit) is that human life begins at conception, and that throughout prenatal development we are dealing with a human person at every stage. For the record, I am rather quirky in believing that this leads consistently to some positions that the political rights tend to champion, like opposition to abortion, infanticide, and euthanasia, but also some other positions that the political left tends to cherish, such as the championing of animal rights or at least a serious view of animal welfare, as well as a general even if not completely absolute opposition to war and to capital punishment. In other words, I think it is only consistent to be pro-life in all possible respects if one believes that society benefits from defining personhood as widely and broadly as one possibly can (being inclusive rather than exclusive about the "grey area" questions and assuming that, if someone might be a person, it is best to act as if s/he is one). That makes me unwelcome on both sides of the political aisle, but so what? I like being a misfit. For more information on these issues, I suggest the thought-provoking little book Veritatis Splendor ["The Splendor of Truth"], by one Karol Wojtyla: see here for some ideas about other books worth reading, or if you don't like my suggestions, start your own list.
You won't find me imposing these views on you; you won't find your grade depending on your agreement or disagreement with that view. But I hope you will find yourself dealing in your own way -- thoughtfully and rationally -- with the philosophical question, "What defines personhood?" and therefore "Who is a person?" The question is not as easy at it sounds; again, thoughtful people can disagree about the best answer to the question, but because it has wide-ranging implications for the kind of society we want to build, it's difficult at times to find (if we should even try to find) compromise solutions to that question.
In other words, it's not my business what you think. But it is my business as an educator that you think (to encourage thoughtful, rational, respectful consideration of issues such as this, regardless of your eventual conclusions)... and to note that one can respect those with whom one disagrees ("The essence of dialogue is not that we relativize our convictions, but that we come to respect one another as persons", Martin Buber).
Clearly, the answers to these questions inform a range of public policy issues -- relating to (for instance) abortion, euthanasia, the stem cell controversy, human cloning, and more. By the time those of you who are 18 to 22 years old are my age (there's no hurry to get there), society will have to have come to terms with these issues in a way that has not happened to date; at present there is no social consensus, and no set of answers that wouldn't alienate some significant social constituency. By then, technology will have vastly outstripped bioethics (or at least any social-cultural consensus about bioethical issues); already, some reputable scientists are starting to talk about "nanotechnology" (the creation of half-human, half-computer beings that, probably, will all end up looking like Lindsay Wagner). If this doesn't scare you, I don't know what does.
The bottom line? You won't be tested or otherwise assessed on your values. (Mercifully, this isn't a philosophy class.) But you will be expected to do some thinking about the value disputes, as well as, of course, the scientific, observable facts that underlie them.
We now return you to your regularly scheduled lecture.