Catholic Medical Quarterly

The Journal of the Catholic Medical Association (UK)

Building knowledge. Building faith. Protecting the vulnerable.

Catholic Medical Quarterly Volume 63(2) May 2013

Natural Law (and the Laws of Nature)

Michael Schutzer-Weissmann

Photo of authorMost people know what is meant by the Laws of Nature and could give a reasonable account of what they are.  Few people would be able to do the same with Natural Law and many would not accept that there is such a thing.

It is not surprising that there is much confusion these days about the Natural Law.  We are all used to hearing talk about obedience to the laws of Nature in scientific contexts without reflecting that such talk is profoundly metaphorical.  Most things in nature, whether they are the planets in their solar orbits or beetles knocking their heads out on oak beams, do not actually “obey” laws any more than the internal angles of a triangle willingly submit to being the sum of two right-angles.  Most of the natural world moves, lives, grows, eats, sleeps, procreates without the knowledge of any injunction to do so, and neither obeys nor disobeys any laws.  We talk of obedience to the laws of Nature because the things of Nature act in certain ways and not in others, as though they were acting in accordance with laws imposed upon them, laws which are their very nature.

Rational thought

And we also talk in this way because we – alone among the phenomena of the natural world – can reflect upon the natural world: we can observe how it is constituted, study how it works and speculate upon its causes and purposes.  We are, therefore, both part of the natural world and outside it; we cannot deny that we, too, like the planets and the death-watch beetle, have a nature which has been imposed on us, but it is that very nature which allows us (nay, forces us) to know what it is.  In short, we are by nature endowed with reason. 

This, then, is the first way in which we can speak with sense about the laws of nature.  All things act according to their natures – natures imposed upon them; human reason can observe things acting according to their natures, can deduce how things in nature are from this observation and – whether theist or scientist – can describe how things in nature are in terms of laws.  “How things are” is a modern, catch-all equivalent of what St.  Thomas Aquinas more robustly called “the eternal law”, when he wrote of the Natural Law as being, “nothing else than the rational creature’s participation in the eternal law”[1]. 

According to St.  Thomas, the rational creature – the human being – can within limits know the “eternal law”, which governs all things.  He knows it by reading the Natural Law written in the book of God’s Providence (or, as one might put it, How Things Are). 

The account that St.  Thomas gives of Natural Law is dependent on the premise that “the Natural Law is consequent to human nature"[2].  In essence, then, there is no difference between the Natural Law and the Laws of Nature; for, if planets and plants act necessarily according to the Laws of Nature, human beings are required by the same laws to act voluntarily.  Since it is by virtue of being rational creatures that our nature is human, we are obliged, as it were, to exercise our Reason – that is, to act freely and make choices.  The ‘obligation’ of human beings to act as moral creatures is essentially no different from the necessity of physical creation to ‘obey’ the rules of Nature: we have no choice but to be human.

Family group photoSuppose there were 'people seeds' blowing about all the time.  Suppose anyone killed would come to life again after a month if kept suitably—but unless they did they became literally rooted in the ground like trees.  Suppose everyone changed to the opposite sex at the age of about thirty.  There would be different rules of behaviour; moral virtues and vices would involve different actions from what they involve in our lives as they are.[3]

In other words, being who we are determines how we must act.  Thus, according to St Thomas Aquinas, the Natural Law derives from the fact of our humanity: “the rule and measure of human acts is the reason, which is the first principle of human acts”[4]. 

Natural Law is “natural”

So, Natural Law is “natural” because it is a law declared by reason – a fact of our human nature – rather than by revelation.  The Laws of Nature are written in the physical world for scientists to read; the Natural Law is written in the human heart (or Reason) for humans to practise.  Where else but in the human heart – in human reason – would there be written those things which are specific to human nature? For it is human nature alone of natural things to make choices; to be moral creatures is of our nature.

Our very nature is the book in which the laws of human morality are written.  That is why it is proper to speak of the Natural Law: “natural”, because written in our nature; “law”, because we can choose to obey or disobey.  In a different, but related sense, St.  Thomas talks (as do the authors of Holy Scripture) of the Natural Law as being inscribed in the hearts of men; but what is written in our hearts is really an understanding of what we have read in God’s Providence.  Thus, knowledge of things as God has ordained them (including our own nature) constitutes a book of laws no less binding on humankind than that which arrived by special delivery from the summit of Mount Sinai, the revealed law entrusted to Moses and the Chosen People of Israel.

The distinction between Revealed Law and Natural Law is neatly summed up by John Milton in Paradise Lost, when Eve – just before she succumbs to the infernal tempter – confidently informs him why it is out of the question that she should follow his advice and taste the forbidden fruit.  Precisely because it is forbidden:

But of this tree we may not taste nor touch;
God so commanded, and left that Command

Sole Daughter of his voice; the rest, we live
Law to our selves, our Reason is our Law.[5]

Milton is also at pains to give an explanation as to why obedience to the Natural Law – even as practised by our pristine ancestors – was an inadequate protection for their perfect innocence:

But God left free the Will, for what obeys
Reason, is free, and Reason he made right,
But bid her well beware, and still erect,
Lest by some faire appearing good surprised
She dictate false, and misinform the Will.[6] [ 355 ]

Creative reason

‘Because I say so’ is not regarded as an injunction binding on rational creatures.  Except, of course, when it is God who says so.  In Milton’s account of the Fall of Man might be seen the dislocation of Natural Law from Revealed Law which can also be seen as a major factor in the moral chaos of our own times.  Speaking as one who has suffered personally from attacks made from the standpoint of theologies resistant to any dilution of what they perceived to be the revealed laws of God, Pope Benedict XVI has recently reminded the world that,

Unlike other great religions, Christianity has never proposed a revealed law to the State and to society, that is to say a juridical order derived from revelation.  Instead, it has pointed to nature and reason as the true sources of law – and to the harmony of objective and subjective reason, which naturally presupposes that both spheres are rooted in the creative reason of God …
… For the development of law and for the development of humanity, it was highly significant that Christian theologians aligned themselves against the religious law associated with polytheism and on the side of philosophy, and that they acknowledged reason and nature in their interrelation as the universally valid source of law.  This step had already been taken by Saint Paul in the Letter to the Romans, when he said: When Gentiles who have not the Law [the Torah of Israel] do by nature what the law requires, they are a law to themselves...  they show that what the law requires is written on their hearts, while their conscience also bears witness...  (Rom 2:14f.)[7]

Pope Benedict XIV also noted what might be metaphorically termed the ‘negative image’ of this separation between what God has revealed and what Reason informs us:

There is another less visible danger, but no less disturbing: the method that permits us to know ever more deeply the rational structures of matter makes us ever less capable of perceiving the source of this rationality, creative Reason.  The capacity to see the laws of material being makes us incapable of seeing the ethical message contained in being, a message that tradition calls lex naturalis, natural moral law. 
This word for many today is almost incomprehensible due to a concept of nature that is no longer metaphysical, but only empirical.  The fact that nature, being itself, is no longer a transparent moral message creates a sense of disorientation that renders the choices of daily life precarious and uncertain. 
… It is precisely in the light of this contestation that all the urgency of the necessity to reflect upon the theme of natural law and to rediscover its truth common to all men appears.  The said law, to which the Apostle Paul refers (cf.  Rom 2: 14-15), is written on the heart of man and is consequently, even today, accessible.[8]

photo of sunsetAnyone who hopes to find in the Natural Law a handy moral tick-box may be disappointed.  The basic principle of the Natural Law, according to St.  Thomas, is to do good and to avoid evil, which seems to be self-evident.  This is precisely St.  Thomas’s point in saying that all precepts of the Natural Law derive from this principle.  For, as he argues – just as the first principle of ontological reasoning is that of being or not-being, so “the first principle of practical reason is founded on the notion of good … that which all things seek after.” [9]

We should be clear, then, that the Natural Law is not confined to particular areas of morality, such as pertain to natural impulses of fear, rage or sexual desire, but embraces all aspects of human activity.  As Elizabeth Anscombe points out in Contraception and Chastity:

Any type of wrong action is "against the natural law": stealing is, framing someone is, oppressing people is.  "Natural law" is simply a way of speaking about the whole of morality, used by Catholic thinkers because they believe the general precepts of morality are laws promulgated by God our Creator in the enlightened human understanding when it is thinking in general terms about what are good and what are bad actions.  That is to say, the discoveries of reflection and reasoning when we think straight about these things are God's legislation to us (whether we realize this or not).[10]

If the Natural Law applies to all moral actions, why does it seem so particularly applicable to sex?

I would answer that, first, sexual activity is the method by which human life is generated and human nature passed from one generation to the next.  Secondly, because it is very closely connected to the Fall of Man; thirdly, because sexual desire is a powerful and universal natural impulse upon which a powerful amount – some would say an excessive amount – of law has been loaded.

If, as has been argued, the Natural Law is intrinsic to human nature we need not fear its disappearance:
the word of authority need no other voice nor strength than procreation.  So long as human beings “go forth and multiply”, the Natural Law, engraved on the human heart, will continue to exist.  Although civilisation may crumble, the just be downtrodden and the human heart hardened, it is of some comfort that while humanity survives, so does the Natural Law.  Lest optimism cloud wisdom, however, let us remember that in procreation we pass on a human nature infected by Original Sin, an infection to which our Reason ia as dangerously prone as are our animal impulses.  The fact of what Bl.  John Henry Newman described as a “terrible, aboriginal calamity”[11] is not universally accepted, but few would argue that there is no connection between sexual activity and human distress.  Some continue to hold on to a version of Freud’s long-since exploded claim that the root of human unhappiness is sexual repression.  Few, I dare say, would not agree that unbridled sexual activity is a universal cause of wretchedness to individuals and damage to society.  It is unsurprising, therefore, that throughout the history of humankind, this is one aspect of human nature to which laws both individual, and social seem most applicable – and one area where “nature” and “law” seem often to be in conflict.

Sexual activity

If it seems, shall we say, ‘natural’, that discussion of the Natural Law inclines towards sexual activity, it is also understandable that the particular instances of sexual activity to which the application of the Natural Law is nowadays almost entirely restricted should be: voluntary celibacy, homosexuality and contraception.

“Doing what comes naturally” – is this not generally accepted as sexual activity? Is it not often employed as an introduction to an excuse for disordered or immoderate sexual activity? Its suggestion would be mysterious were not voluntary celibacy regarded as the epitome of unnatural behaviour.  In modern society there is a particular kind of contempt, pity or suspicion reserved for those who choose to abstain from an active sexual life; and the usual justification offered for such discourteous and ill-considered attitudes is that voluntary celibacy is unnatural.  In the context of the precepts of the Natural Law, nothing could be further from the truth.  Consider: although human sexual behaviour is often rational, it is based on sexual desire, a natural impulse humanity shares with animal nature.  Moreover its impulse is so powerful that it often conflicts with and overthrows the dictates of reason.  Natural Law, as has been shown, derives from Reason, “the rule and measure of human acts.” [12] Hence, to act in accordance with Reason even against natural impulse, is to act more not less naturally with respect to our humanity. 

That conflicts exist between various elements of our composite (human) nature is a fact known not simply to those who believe in the distortion of human nature brought about by the Fall, but through all experience of human life, a conflict not confined to sexual activity:

Though with their high wrongs I am struck to the quick,
Yet with my nobler Reason ‘gainst my fury
Do I take part:[13]

Prospero here is talking of his desire to take revenge on his enemies, a natural impulse he chooses to suppress.  It should be added that voluntary celibacy – consecrated chastity, as it is known – is nor usually a matter of repression but an act of generous charity.  Here, too, we may see that in choosing to deny a natural impulse we share with the animals, the celibate is acting according to the impulse proper to human nature.  For to love is to choose and only rational creatures can choose, just as rational creatures alone can perform, in sexual activity, acts of love.

It was not long ago that “unnatural acts” meant one thing only – homosexual acts performed by men or women.  St.  Thomas Aquinas was aware that there was a question to be answered about this specific use of the phrase “unnatural acts” (or “unnatural sins”): “If all acts of virtue are prescribed by the Natural Law, it seems to follow that all sins are against Nature; whereas this (description) applies to special sins.” His answer is that, although Natural Law refers to all sins as being against Reason, it may also mean, “that nature which is common to man and other animals; and, in this sense, certain special sins are said to be against nature; thus, contrary to sexual intercourse, which is natural to all animals, is unisexual lust, which has received the special name of the unnatural crime.”[14]

If it is not an act of the kind by which procreation may occur it is not sexual intercourse but a different act altogether.

It is interesting to note that St.  Thomas does not speak of homosexual acts as being a form of sinful sexual intercourse, but describes it as being contrary to sexual intercourse.  In making the connection between what animals do and what we do, St.  Thomas is making a point about what sexual intercourse is.  If it is not an act of the kind by which procreation may occur it is not sexual intercourse but a different act altogether – a different act altogether even if it includes pleasure, delight, happiness or love.  This is an important point when it comes to the matter of contraception. 

In Contraception and Chastity[15], Elizabeth Anscombe pointed out that:

If contraceptive intercourse is permissible, then what objection could there be after all to mutual masturbation, or copulation in vase indebito, sodomy, buggery (I should perhaps remark that I am using a legal term here – not indulging in bad language), when normal copulation is impossible or inadvisable (or in any case, according to taste)? It can't be the mere pattern of bodily behaviour in which the stimulation is procured that makes all the difference! But if such things are all right, it becomes perfectly impossible to see anything wrong with homosexual intercourse, for example.  I am not saying: if you think contraception all right you will do these other things; not at all.  The habit of respectability persists and old prejudices die hard.  But I am saying: you will have no solid reason against these things.  You will have no answer to someone who proclaims as many do that they are good too.

It is difficult to appreciate how prophetic this view was at a time when the barrier marked “natural” was still securely in place against homosexual acts and was being rapidly dismantled before contraceptive acts.  It is easy to see why.  In the minds of most people, “unnatural” and “natural” were terms which expressed emotional reaction rather than descriptions of acts.  When the contraceptive pill became widely available in the early 1960’s, the ‘yuk-factor’ associated with contraceptive devices and the barber’s enigmatic enquiries about the coming weekend disappeared.  Most people are still imaginatively resistant to homosexuality but progress, as they say, is being made.

Although Philip Larkin has provided us with a memorable tag for the historical context of the sexual revolution, he was not the only one to note that,

Sexual intercourse began
In nineteen sixty-three …
Between the end of the Chatterley ban
And the Beatles’ first LP[16]

The Church, called to the Second Vatican Council at the end of 1962, knew, of course, that human nature had not suddenly become a different thing in the second half of the twentieth century, but she also knew that there was such a thing as the modern world.  Like Larkin, she knew that it was the advent of the contraceptive pill which had opened the doors into what appeared to many as a brave new world of sanitized sex. 

Into this world, Pope Paul VI released the encyclical Humanae Vitae which re-iterated the Church’s constant teaching on contraception, defending her doctrine against the arguments of the modern world and many of her children by using arguments from the Natural Law:

… God has wisely ordered laws of nature and the incidence of fertility in such a way that successive births are already naturally spaced through the inherent operation of these laws.  The Church, nevertheless, in urging men to the observance of the precepts of the natural law, which it interprets by its constant doctrine, teaches that each and every marital act must of necessity retain its intrinsic relationship to the procreation of human life.[17]
… The reason is that the fundamental nature of the marriage act, while uniting husband and wife in the closest intimacy, also renders them capable of generating new life—and this as a result of laws written into the actual nature of man and of woman.[18]

The timing of Humanae Vitae’s appearance – roughly co-incidental with the widespread availability of the oral contraceptive during the revolutionary and anti-authoritarian Sixties – contributed greatly to the explosion of its objectors’ arguments which filled the air with the heat and dust of righteous indignation.  Had not the Papal Commission set up to re-examine the legitimacy of contraception returned a favourable majority verdict in 1966? Had it not been already been assumed in all the approved circles of intellectual debate (in the manner that has now become so familiar) that no outcome was possible other than that the Pope would declare the use of artificial contraceptives permissible – as though the disappearance of the yuk-factor would clear away any moral objections the Church might have had? The newspaper headlines were ready – “Catholics ready to Swallow Pill”, “Pope says All You need is Love”; the editorials were written: “A new chapter in the history of the Roman Catholic Church was opened today as Pope Paul VI continued his predecessor’s work of letting light into the darkness of dead and bigoted traditions.  In lifting the age-old ban against contraception, the sprightly 71-year old pontiff has brought the barque of St Peter out of the doldrums of tradition into the living waters of the real world, a world inhabited by real people with their real joys and their real problems…”

Over forty years on from those heady days, we can perceive more easily perhaps how a doctrinal volte-face on the matter of contraception would have blown a hole in the foundations of the Church just as it would have puffed away into thin air the concept of Natural Law. 

Many within the Church blamed Pope Paul VI for relying heavily on arguments based on Natural Law.  Humanae Vitae, in falling back on the traditional idea of Natural Law perceived by human reason happily married to the revealed law of God, seemed irrelevant in a world where Nature was not as it had been and in which many questioned the revealed word of God.  Citizens of a public world in which laws are founded on negotiated compromise or majority consent (such as the judgment of Pope John XXIII’s Commission on birth-control) we are becoming strangers to what St Thomas called “the rational creature’s participation in the eternal law” – that is, Natural Law.  Moreover, so radically opposed to any ideas of obligation and submission is our concept of what is “natural” as to make it almost identical with that which is desirable – that which “feels right”.  Hence, despite the efforts of the Holy Father, marriage between Natural Law and the revealed law of God seems as irrelevant to many minds as does the sacred bond of matrimony to many bodies.

When primitive devices were used to ensure that conception would not take place, contraception was widely regarded as an unnatural practice; but this is no longer the case in most people’s minds, particularly when the epithet “artificial” has been discarded.  It is easier to think of contraception being against the Natural Law when preventative artifice (as with physical barriers, etc) is apparent, but many people are mystified to discover that the Roman Catholic Church regards all forms of contraception as being contrary to the Natural Law, including coitus interruptus.  Indeed, this is perhaps the paradigm case of an unnatural act since it is at the point when the act achieves its natural character that it is perverted.  Although the heterosexual contraceptive act may look the same as, what for the sake of convenience I shall call the act of marriage, it is essentially different, different in like manner to the distinction St.  Thomas points out as existing between homosexual acts and sexual intercourse.

Indeed the contraceptive act can be seen as contrary to the Natural Law in ever-deepening profundity.  Unlike any sexual act performed by two people of the same sex, contraceptive intercourse requires the deliberate frustration of the essential nature of what the couple are actually doing.  And that act – the sexual act – is itself the very soul of Nature’s power and activity.  Contraception represents an unspoken yet insistent claim that the nature of sexual intercourse – procreation – is defective (and must be ‘remedied’).

Such thoughts are far from people’s minds when they contemplate or embark on sexual activities, but I would wager that thoughts of preventing natural consequences are very frequently present.  Of all things that humans engage in, few bring us into such intimate proximity with Nature’s power, both in terms of impulse and consequences, as sexual intercourse.  Human survival and happiness depends on our response to the Laws of Nature. 

Human survival and happiness depends on our response to the Laws of Nature.  Our reason instructs us on different occasions and in different circumstances now to subdue, now to submit to her claims and her power. 

Our reason instructs us on different occasions and in different circumstances now to subdue, now to submit to her claims and her power.  According to human will her bounty is harvested and husbanded, or laid waste.  We learn her workings and use her powers to cure or to kill.

It has been humanity’s birthright and inheritance to enjoy Nature’s bounty and to overcome Nature’s dangers.  Contraception strikes against the Natural Law and the Laws of Nature by transforming the former into the latter.

© Michael Schutzer-Weissmann (MASW, English) M.A., late Scholar of Gonville and Caius College, Cambridge.


  1. Summa Theologica, Prima Secundae Parts, 91
  2. Summa Theologica, Prima Secundae Parts, 94
  3. Elizabeth Anscombe: Sin: the McGivney Lectures, first published in Faith in a Hard Ground, 2008
  4. Summa Theologica, Prima Secundae Parts, 90 Art.  1: “Whether the Natural Law is something pertaining to reason”
  5. Paradise Lost, Book IX, 651-4
  6. Paradise Lost, Book IX, 351-5
  7. Benedict XVI, Address at he Reichstag Building, “The Listening Heart: Reflections on the Foundations of Law”, 22nd September 2011
  8. Benedict XVI, Address to the International Congress on Natural Moral Law, 12th February 2007
  9. Summa Theologica, Prima Secundae Parts, 94: Art.  2
  10. Elizabeth Anscombe, Contraception and Chastity, 1972
  11. Newman: Apologia pro Sua Vitae, chapter 5
  12. Summa Theologica, Prima Secundae Parts, 90: Art.  1
  13. The Tempest, William Shakespeare, V, i, 25-7
  14. Summa Theologica, Prima Secundae Parts, 94: Art.  3
  15. First published in The Human World in 1972 and later by the CTS (from which it is till available) in 1975. 
  16. Philip Larkin, Annus Mirabilis, 1968
  17. Humane Vitae, II 11 “Observing the Natural Law”
  18. Humane Vitae, II 12 “Union and Procreation”