The use of human embryonic stem cells (ES cells) raises a number of important issues. One issue that has prompted fierce debate has been the moral status of the embryo. In considering this status, the production of the embryos fetuses must be linked not only to the use of the embryonic material in the laboratory, but to the way in which "natural" reproductive processes "use" embryos. People often believe that there is some moral imperative to be ultra cautious in permitting new research, particularly in the general field of genetics. This has now been elevated into a principle, commonly called "the precautionary principle". It is not unusual to find this so-called "precautionary principle" being invoked in circumstances in which it is far from clear in which direction (if any) caution lies.

We cannot know which way lies caution without having some rational basis for establishing the scale of likely dangers from pursuing stem cell research and comparing those with the ongoing costs of failing to pursue the research to a successful conclusion. These costs may include the vast numbers of people dying for want of donor tissue and organs or from other diseases for which ES cells might prove therapeutic. What is clear is that, with hundreds of thousands, perhaps millions, of people dying annually world-wide from damaged organs and tissue and from diseases such as diabetes, neuro-degenerative disorders, and heart disease; any possible dangers accruing from ES cell research would have to be "real and present" before any moratorium or delay could be defended on ethical or even precautionary grounds. It is unclear how ES cell research presents any real and present dangers, (with the possible exception of loss of popularity by politicians).

Since stem cells, which might be used for research and therapeutic purposes, can, at present, only be obtained either from aborted fetuses or from pre-implantation embryos their recovery and use for current practical purposes turns crucially on the moral status of the embryo and the fetus.

Many believe that embryonic stem cells will always be the best type of stem cells to use, because they have proven and well researched characteristics compared to other sources of stem cells. It is therefore likely to be and remain important to see whether the use of human embryos and fetuses as sources of cells is morally objectionable.

There are three possible solutions to the ethical problems of using human embryonic stem cells. The first is the use of cells from the early embryo that survives the removal of such cells; the second is the deployment of arguments about the moral status of the embryo. This is the line taken for example by the CMO's Expert Group in the United Kingdom, which relies on a moral distinction, used in previous legislation and regulation, between the early embryo prior to the development of the primitive streak at around fourteen days development and later stages of embryonic development. The third solution is a reminder about the role of embryo loss in reproduction.

It is possible to remove cells from early pre-implantation embryos without damage to the original embryo. This may be one solution to the problem of obtaining embryonic stem cells. However, if the cells removed are toti-potent, (capable of becoming literally any part of the creature including the whole creature) then they are in effect separate zygotes, they are themselves "embryos" and so must be protected to whatever extent embryos are protected. If however, such cells are merely pluri-potent (capable of development in many ways but not in all and not capable of becoming a new separate creature) then they could not be regarded as embryos and the use of them would, presumably, not offend those who regard the embryo as sacrosanct. Unfortunately it is not at present possible to tell in advance whether a particular cell is toti-potent of simply pluri-potent. This can only be discovered retrospectively by observing the cells capabilities.

While everyone has views about the moral status of the embryo and some of those who have views even have arguments to support their views, attempts to solve problems about issues that depend on the use of embryonic or fetal material by recourse to establishing the moral status of the embryo have proved intractable. Arguments about the moral status of the embryo are convincing and in some cases conclusive, however, notoriously they fail to persuade the groups crucial to achieving consensus on vexed policy issues. Most people are neither puzzled as to the moral status of the embryo or fetus, nor do they welcome arguments which challenge their views. What they seek from philosophical reflection on these issues is not enlightenment but confirmation of prejudice.

While this may appear a depressing conclusion, I believe that progress in the field of social policy may still be made. This is because many members of these same groups, and if not them, then certainly established principles and practices in the societies in which they live and to which they owe allegiance, are committed to policies which indicate the permissibility and acceptability of a number of crucial practices.

I will try now to indicate what follows about the ethics of the use of ES cells from practices or principles that are well established in many of the relevant societies, and these will of course include societies with the capacity to pursue such research. This involves exploration of the third way. We will start with the ethics and law of human reproduction.

While there are of course better or worse reasons for creating an embryo or establishing a pregnancy, people who can do so without medical assistance are not usually required either to provide reasons or to qualify for the right or liberty to do so. I will assume that the practice of refraining from interfering with unassisted reproduction is both morally defensible and legally acceptable, and that public policy on reproductive liberty for the consenting fertile is unlikely to change. Even the use of assisted reproductive technologies (ART) is now commonplace and although in some circumstances parents have to demonstrate their fitness (for example in the U.K. under the Human Fertilisation and Embryology Act 1990 doctors must take account of the welfare of the child to be born as a result of using the technologies) the creation of embryos using ART is very common and subject to relatively few restrictions.

Let us start with the free and completely unfettered liberty to establish a pregnancy by sexual reproduction without any "medical" assistance.

What are people and societies who accept this free and unfettered liberty committing themselves to? What has a God who has ordained natural procreation committed herself to?

We now know that for every successful pregnancy that results in a live birth many, perhaps as many as five early embryos will be lost or "miscarry" (although these are not perhaps "miscarriages" as the term is normally used, because this sort of very early embryo loss is almost always entirely unnoticed). Many of these embryos will be lost because of genetic abnormalities but some would have been viable. How are we to think of the decision to attempt to have a child in the light of these facts? One obvious and inescapable conclusion is that God and/or nature has ordained that "spare" embryos be produced for almost every pregnancy, and that most of these will have to die in order that a sibling embryo can come to birth. Thus the sacrifice of embryos seems to be an inescapable and inevitable part of the process of procreation. It may not be intentional sacrifice, and it may not attend every pregnancy, but the loss of many embryos is the inevitable consequence of the vast majority (perhaps all) pregnancies. For everyone who knows the facts, it is conscious, knowing and therefore deliberate sacrifice; and for everyone, regardless of "guilty" knowledge, it is part of the true description of what they do in having or attempting to have children. We may conclude that the production of spare embryos, some of which will be sacrificed, is not unique to ART; it is an inevitable, (and presumably acceptable, or at least tolerable?) part of all reproduction.

Is it a blessing that in the present state of technology all of these spare embryos, by-products of natural sexual procreation, are lost, for the most part unnoticed and their stem cells irretrievable and unusable? If, perhaps per impossibile, we found a way of monitoring and collecting stem cells and perhaps other usable material from these early miscarriages, would there be any ethical objection to our so doing? I shall assume for the moment that this is a rhetorical question because the answer is clearly that it is not a moral advantage that no stem cells are recoverable from this process, it is merely an unfortunate fact.

It might be responded that mothers do not usually wish or intend the death of their embryos when they become pregnant (although many who conceive will not have wished to become pregnant) and that this process cannot therefore reasonably be compared to the deliberate creation of spare embryos for research or therapy, or the deliberate use of embryos, which might otherwise be implanted. There are important differences of course, but it is not clear that these differences are material.

Both natural procreation and ART involve a process in which embryos, additional to those which will actually become children, are created only to die. I will continue to call these "spare" embryos in each case. If either of these processes are justified it is because the objective of producing a live healthy child is judged worth this particular cost. So far we will assume that the purpose in each case is the securing of a successful pregnancy and a new live human child.

The intentions of the actors, appealed to in the frequently deployed but fallacious doctrine of double effect are not here relevant. What matters is what the agents knowingly and voluntarily bring about. That this is true can be seen by considering the following example.

Suppose we discovered that the use of mobile phones within fifty metres of a pregnant woman resulted in a high probability, near certainty, of early miscarriage. No one would suggest that once this is known, it would be legitimate to continue use of mobile phones in such circumstances on the grounds that phone owners did not intend to cause miscarriages. Any claim by phone users that they were merely intent on causing a public nuisance or, less probably, making telephonic communication with another person and therefore not responsible for the miscarriages would be rightly dismissed. It might of course be the case that we would decide that mobile communications were so important that the price of early miscarriage, and the consequent sacrifice of embryos, was one well worth paying for the freedom to use mobile phones. And this is, presumably, what we feel about the importance of establishing pregnancies and having children. Mobile phone users of course usually have an alternative method of communication available but we'll suppose they do not.

To be sure, using a mobile phone is trivial by comparison with the moral significance of creating a new human life, and it might be argued that the comparison is misleading; however the point of the analogy lies elsewhere. This example shows the incoherence of the so-called doctrine of double effect. The motives or primary purposes of the phone user are clearly irrelevant to the issue of their responsibility for the consequences of their actions. They are responsible for what they knowingly bring about. The only remaining question is as to whether given the moral importance of what they are trying to achieve (phoning their friends) the consequent miscarriages are a price it is morally justifiable to exact to achieve that end. Here the answer is clearly "no". However when we pose the same question about the moral acceptability of sacrificing embryos in pursuance of establishing a successful pregnancy the answer seems different. My point is that the same issues arise when considering the use of embryos to obtain ES cells. Given the possible therapeutic uses we have reviewed, it would be difficult, I suggest, to regard such uses as other than morally highly significant.

We may conclude that there can be no absolute prohibition on the conscious, voluntary destruction of human embryos in pursuit of a particular morally important goal: that of producing a live healthy child.

In the United States, current federal law prohibits the use of federal funds for "the creation of a human embryo" explicitly for research purposes or, more crucially, for "research in which a human embryo or embryos are destroyed, discarded or knowingly subjected to the risk of injury or death" (Pub.L. 1998). Such law is presumably animated by concern about the morally problematic nature of such actions. As we have noted, normal sexual reproduction inevitably involves a process in which "a human embryo or embryos are destroyed or discarded". It is also incontrovertibly an activity in which "a human embryo or embryos" are "knowingly subjected to the risk of injury or death"; at least for anyone who knows the facts of life. It is interesting that the framers of this federal legislation chose to concentrate on the "knowing" rather, than say, the "intended" risk of injury or death to embryos. It seems natural to regard this as some evidence that the framers of this legislation implicitly accept a premise of this argument; that it is the knowledge of consequences that carries with it responsibility, and not the more narrow idea of intending or willing those consequences as a primary objective of decisions or conduct.

The conscious voluntary production of embryos for research, not as the by-product of attempts (assisted or not) at reproduction is a marginally different case, although some will think the differences important. However, if the analysis so far is correct, then this case is analogous in that it involves the production and destruction of embryos for an important moral purpose. All that remains is to decide what sorts of moral objectives are comparable in importance to that of producing a child.

Although some would defend such a position, some preference utilitarians for example, it would seem more than a little perverse to imagine that saving an existing life could rank lower in moral importance to creating a new life. Assisted reproduction is, for example, given relatively low priority in the provision of health care services. Equally, saving a life that will exist in the future seems morally comparable to creating a future life. In either case the moral quality and importance of the actions and decisions involved and of their consequences seem comparable.

This article is an edited version of a paper to be published in A Companion to Genethics: philosophy and the genetic revolution, available from Amazon UK. Professor Harris presented a version of this paper to the British Humanist Association's Manchester conference.