In some people's eyes, the very idea that this should be a conscience matter is still incomprehensible, even somehow offensive.  If this is simply a set of practical proposals whose results could be the cure of various terrible diseases, what business is it of anyone's private conscience to try and stop them?  Isn't this, some commentators ask, just one more example of religious bigots seeking to impose their irrational views on the rest of us?"

It's worth trying to spell out just why issues of conscience do arise. Some of the questions could perhaps be answered by a better understanding of what the science does and doesn't mean.  But it's quite important also to say that science in itself is never going to be able to tell us what the right thing is for us to do; it can only tell us what's possible.  And, in spite of the way some people talk in this debate, there really is a difference between what's possible and what's right.

So where is the big question for consciences?  In most people's understanding of what counts as moral behaviour, it's taken for granted that you don't use anyone else just for your own purposes – or even for other people's purposes.  A human person, an individual body with feelings and thoughts, needs to be treated, as we sometimes say, as an end in itself, not a tool for someone else's agenda.

So we condemn rape and torture and blackmail of various sorts.  We don't allow experiments on people's bodies or minds without their consent. And we don't breed human individuals to create a pool of organs that could be transplanted to save the lives of others.

Here's where the problems begin.  If a human embryo is produced by non-reproductive cloning, created as a research tool, as proposed in the Bill and then destroyed, is this in the same category as using someone's body as an instrument for your purposes?  Put like this, the answer is clearly no. The compassionate and responsible scientists we are discussing here are far removed from the nightmares of experimentation on living and unwilling subjects that haunt our imaginations.  The difference is clear and no-one should be trying to make debating points along these lines.

But if you put it another way and talk about creating an embryo that could in principle become a distinctive person - because it is already a distinctive organic unity - could this in the long run encourage a drift towards a new attitude to human life – an attitude that was more and more fuzzy about the absolute right of an individual not to be used for the purposes of another?

This is what worries some commentators about the practice of non-reproductive cloning – and it also raises worries in connection with the creation of 'saviour siblings', babies brought into being so that there is compatible genetic material that can be used therapeutically for a brother or sister with a major disease or disability.  This is one of the most poignantly difficult areas in the whole discussion; but we have to ask what the implications are of bringing a life into being primarily in order to solve another's problem.

So I believe these are the most difficult issues around the Bill's provisions.  I am yet to be convinced that the measures relating to non-reproductive cloning will not open the way to a less consistently respectful attitude to life or that those concerning 'saviour siblings' similarly protect against a person being treated primarily as a tool for another's ends. These matters need further serious debate. 

This doesn't mean that we are bound to think of the primitive embryonic material as in every sense a 'person' – but it does mean that we can't lose sight of the fact that this organic unit is a potential person, and that the decisions we make about it are decisions about possible human and personal futures.  This is also why I welcome the pressure from some quarters to take this opportunity of reducing the time limits for abortion. And I suspect that a good many who could just about manage to live with the use of embryonic material produced in the course of IVF treatment - embryos that are never going to be implanted - would still find the deliberate creation of new embryos solely for research unacceptable.

The case of the 'hybrid embryo' is one that I frankly find confusing.  I don't know in what sense this blending of human and animal material is strictly an embryo, rather than just a laboratory creation.  Scientists seem to be unclear as to whether such an embryo would actually be capable of being implanted.  If it isn't, the problem is lessened; if it is, the problems are manifold, and it's not quite enough to be told that implantation would not be allowed.

I recently heard one senior scientists say that the objections made on the grounds of conscience to some aspects of embryo research were actually very important for science itself.  Because most scientists have real reservations about relying on creating embryos in the lab for research, they are sensitive to the challenges made on the grounds of conscience – and this drives them to harder and harder work on alternatives, work that is bearing much fruit in the reprogramming of adult cells.  This technique has turned out to have major therapeutic advantages in many cases, as well as being morally more straightforward.  Challenge or restriction in one area can be constructive.

Conscientious objections about the Bill are not a matter of blind superstition.  They arise from serious concerns about where the direction of some sorts of research might one day lead society.  'Slippery slope' arguments don't settle the question, but they can't be ignored.  And I, for one, am grateful that both scientists and politicians are willing to recognize that there is a serious debate to be had on these matters of conscience, and more is at stake than just a set of irrational prejudices.