Two weeks ago I speculated on some attitudes towards sexuality within the Church. And excellent and helpful comments ensued. But I was aware that I was confining myself to a relatively straightforward aspect: our recognition – with or without the Church’s help – of the ways in which sexuality could be used in an unloving fashion. Here I want to look at the knottier question of the intrinsic nature of human sexuality laid down by God.

Imagine for a moment that you are exploring the far corners of an attic in an old house, and that you come across a piece of machinery which you don’t recognise. It’s heavy, it has a handle to turn, and it has numbers that can be set and changed. By observation of how its parts work, and by experiment, you eventually discover that it is a mechanical calculator with which quite complex multiplication and division can be done. You now know what its maker designed it for. Of course, being an inanimate possession, you are free to use it as you wish – for its maker’s purpose perhaps, or as a curiosity to display, or an effective door stop.

Now transfer that example to sexuality. It doesn’t take a genius to work out in an analogous way the purpose of our sexual equipment. The biology shows clearly that it is structurally ordered toward the conception of new members of the species, and that the parts are fitted for congress between male and female. We may find further – with experience – that the sexual drive urges us towards congress, and so conception; and that it also has the tendency to bind the participants into a long term relationship which enables them to support each other in practical and psychological ways through the task of parenthood.

Here the analogy with the calculator breaks down. We are not objects which we possess and can dispose of as we wish. Our human nature is given to us by God, the divine maker. So we are obliged to use our sexuality according to the nature he gave us. And it pays us to do so because – as Aristotle said and Aquinas confirmed – in order for an entity to flourish it must work in accord with its nature.

This analysis of vice and virtue through physical nature has traditionally been given preeminence in moral theology. Thus, for example,  Aquinas says, “In every genus, worst of all is the corruption of the principle on which the rest depend. Now the principles of reason are those things that are according to nature, because reason presupposes things as determined by nature, before disposing of other things according as it is fitting…in matters of action it is most grave and shameful to act against things as determined by nature. Therefore, since by the unnatural vices man transgresses that which has been determined by nature with regard to the use of venereal actions, it follows that in this matter this sin is gravest of all.”

This does not refer merely to “venereal actions”, although this is where it is most frequently encountered. It applies for instance to physical mutilation, or to telling lies – where, if you take this approach, you are abusing the purpose of the God-given power of speech which no motivation, however compelling,  can excuse .

This deduction of intrinsic moral status from a primarily physical point of view still reflects the official position although its alleged shortcomings have made it increasingly unpopular. One reason is that its unconditionality leads to moral positions which are counterintuitive. For example, a strict application would forbid the donation of a kidney between living people; the Catechism makes it clear that not even the avoidance of grave injustice to a third party can justify a lie – although deceit can be used in other ways, and – the most topical example – the prohibition of condoms for a married couple who are serodiscordant.

A second reason for unpopularity is that the biological criterion of morality alone fails to do justice to the whole of human nature. This was more understandable in Aquinas’s day when we knew so little about the psychological aspects of the human being. So when we ask ourselves what course of action should we follow or avoid so that we can flourish in the way that God intended it is not surprising that the 21st century answer differs in some aspects from the 13th.

I certainly would not argue that physical biology is a useless guide. It will always be a strong indicator of the way in which we should behave. Thus the power of speech, needed for us to fulfil our natures as social beings, indicates that truth-telling is of the highest importance but not necessarily without the possibility of exceptions. The sexual organs still indicate that flourishing is best achieved through heterosexual behaviour linked to generation and the commitment of marriage.

Perhaps our focus should move away from looking at all the things which we get wrong, and be applied to the positive values. That way we speak to man’s aspirations rather than to his fears. What is historically certain is that our continued cataloguing of sexual sin has not led to more orthodox behaviour. But it has led to our ill repute, and our rejection in the market place. I will settle for John XXIII’s remarks at the beginning of the Council: “Nowadays, however, the spouse of Christ prefers to make use of the medicine of mercy rather than that of severity. She considers that she meets the needs of the present day by demonstrating the validity of her teaching rather than by condemnations…”