The President's Council on Bioethics click here to skip navigation


Human Dignity and Bioethics: Essays Commissioned by the President's Council on Bioethics

The President's Council on Bioethics
Washington, D.C.
March 2008

Part 1: Dignity and Modern Science

Commentary on Dennett

Alfonso Gómez-Lobo

In this note I would like to address a single issue in Professor Dennett's paper. I decided to do it not because I consider his views on this particular question in any way offensive or subversive, but because I find them rather perplexing on his own assumptions. First, I should say in truly Socratic fashion where I think there is sufficient agreement for the conversation to take place. I have a positive appreciation of science and I do not see scientific truth as in any way a threat to anything I hold dear. I wholeheartedly admit bona fide scientific evidence as a valid move in the dialogue. On the other hand, I hesitate to accept the extrapolation of scientific results beyond the self-imposed limits of science itself, as well as arguments based on the mere existence of a technological practice.

The issue I want to examine is whether the following claims by Professor Dennett are true or false:

The questions of when (human) life begins and ends.are, according to science, more like the question of the area of a mountain than its altitude above sea level: it all depends on what can only be conventional definitions of the boundary conditions. Science promises-or threatens-to replace the traditional absolutes about the conditions of human life with a host of relativistic complications and the denial of any sharp boundaries on which to hang tradition. 1

The above claims are important to the contents of this volume because, if true, they leave us in the position of Plato's bad butcher: we would have "to splinter a limb (or part, meros ) into pieces" since there would be no "natural joints ( arthra )" at which to effect the proper cut.2 In other words, there would be no way of deciding objectively whether very young (and very old) human beings have inherent dignity and therefore should be respected. This would be a purely "conventional" matter, i.e., something to be whom? By the majority (which often means by the most powerful and influential within that group)? By right-wing politicians? By left-wing ideologues? This, of course, makes it extremely difficult, in my view, "to ensure that the values we defend deserve the respect of all," as Professor Dennett rightly demands.

How does Professor Dennett argue for his claims? He first gives us a picture of the "wonderful taxonomies" science has given us. He even uses Plato's imagery and terminology: "[Science has].articulat-ed [from arthra ] and largely confirmed a Tree of Life that shows why 'creature with a backbone' carves Nature better than 'creature with wings.'" And then he adds: "But the crisp, logical boundaries that science gives us don't include any joints where tradition demands them. In particular, there is no moment of ensoulment to be discovered in the breathtakingly complicated processes that ensue after sperm meets egg and they begin producing an embryo.."

The last statement is puzzling. Surely Professor Dennett does not speak of ensoulment in his own voice. In other parts of his text he rejects Cartesian dualism and also seems to reject dualism altogether. But the notion of ensoulment requires dualistic assumptions: only if there is one substance, a body, and a different substance, a (Cartesian) soul, does it make sense to claim that a soul comes into a body that previously was not human and now makes it human.

If someone rejects dualism (and I think this can only be done by means of metaphysical arguments and not by merely scientific ones) then the natural position to adopt is a form of monism, the view namely that we are a single integrated substance that is alive and that, at a certain stage of maturity, will exhibit certain mental activities that we associate with freedom and reason. On this approach the soul can be understood not as a separate entity that comes to occupy the body, but as the genetic information contained in the DNA that provides the dynamism for the development of a human organism.

The view just presented is not only consistent with present-day science, it also allows us to see that talk about "a mere bundle of living human tissue becoming a person" is a remnant of the rejected dualistic metaphysics. This discredited picture requires one substance, "a mere bundle of living human tissue," what biology textbooks would more accurately call "an embryo" or "a fetus," and a second item that was not previously there, not even in latent form, that provokes a drastic change, a change that ex hypothesi does not preserve the sub-stance's identity. Since the previously existing organism continues to exist after the arrival of the new item, the resulting "person" would be a new entity, a composite of the body and something arriving at a later point in time.

It makes much better sense to accept the scientific evidence, under the assumption that each one of us is essentially an integrated human organism. On this view, the gradual changes that take us to adulthood seem to preserve identity (we say that it is the same organism that is growing and maturing), and those changes may be interpreted as a successive activation of functions that were already latent "in the genes." None of this is old myth, and all of it is consistent with present common knowledge.

Let us press on and ask whether contemporary science shows gradualism or a clear articulation at the inception of a human life. Since I am not a scientist, I am here relying on biology and embryology textbooks in use at American universities.3 The picture that emerges, in summary, is this: through meiosis human organisms produce gametes, that is, cells that have half the standard number of human chromosomes. Each gamete (either sperm or egg) is a specialized cell that lies at the end of a line of development and is thus unipotent. By itself it cannot go any further. Neither an egg nor a sperm is an organism, and each of them is destined to die within a short period of time. If, however, a sperm manages to penetrate the zona pellucida of the egg and the two fuse, then a radical change takes place: a new cell emerges that stands at the beginning of a line of development. It has the full complement of human chromosomes and is strictly totipotent. There is no gradualism here of the sort found in the emergence of a new species nor a process analogous to the "coming of age." The empirical evidence shows that the gametes cease to exist and a zygote, the first stage in a new organism, begins to exist within a short period of time.

There is much more in the embryology literature that could be quoted, but this suffices to make Plato's good butcher happy: here we have uncovered an arthron , an "articulation" or "joint," that allows him to make an elegant cut.

What this entails for the defense of values that deserve the respect of all is this: no scientific progress is sufficient to make us abandon the rational moral conviction that it would be wrong intentionally to kill an innocent adult human being. If we reject dualism as part of the old myths and accept the basic, commonsense conviction that we are unified human animals, then we should accept that as long as we are alive we are the same being,4 and if an adult is endowed with dignity then it follows that he or she also was endowed with dignity in earlier phases of his or her life, back to the beginning. I submit that this conception of the acknowledgement of dignity deserves the respect of all because in principle no human being is excluded.



1. From Dennett's essay in this volume, p. 40.

2. Phaedrus 265e.

3. Cf. Neil A. Campbell and Jane B. Reece, Biology , 6th ed. (San Francisco, California: Benjamin Cummings, 2002); William J. Larsen, Essentials of Human Embryology (New York: Churchill Livingstone, 1998); Keith L. Moore and Trivedi V. N. Persaud, Before We Were Born: Essentials of Embryology and Birth Defects , 6th ed. (Philadelphia: Saunders, 2003).

4. Some people reject the trans-temporal identity of an adult and the zygote he or she once was on the basis of the possibility of twinning. A critique of this view is offered in Gregor Damschen, Alfonso Gómez-Lobo, and Dieter Schoenecker,"Sixteen days? A reply to B. Smith and B. Brogaard on the beginning of human individuals," Journal of Medicine and Philosophy 31 (2006): 165-175.

Next Chapter Right Arrow

  - The President's Council on Bioethics -  
Home Site Map Disclaimers Privacy Notice Accessibility NBAC HHS