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Updated: May 8, 2023

There is no single theory of natural law, but rather a number of theories linked by certain common assumptions. Central to these is the assertion that there are certain objective moral principles which can be discovered by reason and according to which man ought to behave. These principles are universal, unchanging and absolute, and remain objectively true even if they are ignored, misunderstood or abused.


The study of natural law is valuable inasmuch as it turns our attention away from the historically fortuitous features of human legal systems to the universal (or near-universal principles) which underlie them. It can make us stop to consider why we have laws at all, what they can achieve, and what we should do when the law fails and perpetrates injustice. The primary attraction of natural law to the modern thinker is that it makes room for the argument that there may in some circumstances be a higher duty than mere obedience to the laws of the state. Such an argument has been raised intermittently throughout history, but featured largely in the Nuremberg War Crimes Trials and so re-awakened interest in the natural law philosophy.

If we are to categorise certain laws as unjust, however, certain basic questions arise.

  • What makes a law unjust? Aquinas said a just law was one which served the common good, distributed burdens fairly, promoted religion, and was within the law-maker's authority, but these are value-laden criteria and open to argument in any given case.

  • Who decides whether or not a law is unjust? If natural law is truly objective and ascertainable by reason, then such a decision should be open to anyone and not just to lawyers, but the practical consequences of that are alarming.

  • What if a particular law is unjust? Should the citizen obey it even so, for fear that disobedience would bring the law as a whole into disrepute? And should the judges apply such a law or simply ignore it?

The question of civil disobedience - disobedience to unjust laws - is one that has troubled natural lawyers throughout the ages. Some have tried to justify such disobedience as lawful, even where it involves the use of violence, if the activity or law under attack is demonstrably contrary to natural law.


At the heart of the natural law philosophy lies the idea that there are certain universal and unchanging moral principles, and we may therefore ask how we are to discover these principles? Various approaches have been suggested by different writers, though each of them has certain flaws.

The classical approach is that by observing what happens in nature we can deduce what ought to happen. Thus, for example, it is natural for all creatures (including man) to reproduce themselves, and so we may deduce a principle of natural law that man ought to reproduce. This is no mere illustration, but one of the arguments deployed by Pope Paul VI in Humanae Vitae to justify the assertion that every marriage act must remain open to the transmission of life. Hume and other critics would reply that such logic confuses description with prescription, and makes an unwarranted leap from what is to what ought to be. However, even the positivist Hart admits that in everyday thought and there is a tendency to deduce "ought" from "is". We regard an abnormal state of affairs as "wrong", and suggest that children "ought" to develop at a certain rate or that urine "ought" to be a certain colour, simply because this is what usually happens. (This is not only a linguistic matter - if such an "ought" is not obeyed we become worried and send for the doctor.) Similarly, in matters of sexual morality society tends to approve of practices which are common and disapprove of those such as homosexuality which deviate from the norm.

A second approach is the teleological one which assumes certain natural predetermined ends. In Aquinas' case this is God's plan for the universe, while Finnis adopts a secular approach with his seven "basic goods", and claims that the natural law is concerned with the promotion of these. Such approaches do not suffer the logical failure of the classical approach, but they do require acceptance of the pre-asserted ends as being those which are indeed objectively desirable irrespective of time or place.

Hart has suggested a "minimum content of natural law" based on biological and psychological observation. He notes certain truisms about human nature - human vulnerability, approximate equality, limited altruism, limited resources, and limited understanding and strength of will - and assumes a commitment to survival; from these, he claims, we can work out a set of essential principles to enhance our chances of survival and to protect persons, property and promises. This is not to say that a legal system must logically include Hart's minimum content, but only that as a matter of practical efficiency it is unlikely to succeed unless it does so. This may perhaps be seen as an alternative teleological approach, with the difference that Hart's "end" is physical survival rather than eternal life. Our concern is with the social arrangements for continued existence, he says, not those for a suicide club.

Some writers begin by asserting as self-evident the natural law principles themselves: we hold these truths to be self-evident, begins the American Declaration of Independence, that all men are created equal, that they are endowed by their Creator with certain unalienable rights, that among these are life, liberty and the pursuit of happiness. The problem with this approach is that what is self-evident to one society may not seem so to another: we might agree in twentieth-century England that slavery is wrong, but this was by no means self-evident in eighteenth-century America or pre-Christian Greece. The modern jurist Rudolf Stammler has suggested that the content of natural law may therefore vary from one society to another, but this is wholly inconsistent with our earlier definition.

It is appropriate at this point, however, to set aside our general discussion of the natural law approach to consider something of its history. Finnis and other natural lawyers would claim that natural law is eternal and so has no history, but that we can nevertheless consider the history of legal doctrines which have asserted the existence of principles of natural law.


The ideas of natural law are very old, and can be traced back more than two thousand years. Even before Aristotle (384-322 BC) the idea was around that human laws had their place in the order of things, but he and the Stoics argued that man could apply his own reason to the state of nature to develop principles of morality and natural justice which would be universal, unchanging and natural. These Greek ideas spread to Rome, and Cicero (106-43 BC) said that true law was right reason in agreement with nature ... it was a sin to try to alter this law or to repeal any part of it, and it was impossible to abolish it entirely. The natural law, he felt, was a higher law by which the validity of positive law was to be measured. Logically, therefore, an unjust man-made law in opposition to natural law was not truly law at all.

The spread of the Roman Empire created a need for some system of law, simpler and wider-ranging than the jus civile of Rome, to regulate dealings between Romans and strangers or between strangers. Justinian remarked that throughout the known world every people ... used partly a law peculiar to itself and partly a law common to all mankind, and so the jus gentium was therefore created as a universal code of law applicable throughout the Empire. This was recognised by Aquinas and most other writers as a man-made code, however, and not to be confused with natural law.


The principal exponent of natural law ideas in the middle ages was Thomas Aquinas (1224-1274), who (according to Finnis) occupies a uniquely strategic place in the history of natural law theorising. In his major work Summa Theologica Aquinas distinguished between

  • Eternal law - the rational guidance of God, necessary since man is ordained to a particular end (eternal happiness) and cannot attain this through his own powers alone;

  • Divine law - the part of eternal law that has been revealed to man through the Holy Scriptures;

  • Natural law - the participation of rational creatures in the eternal law, by use of man's reason to discover that part of eternal law which applies to the human condition; and

  • Human law - laws made by man (in accordance with divine law and natural law) to regulate society so that man can live in harmony with his fellows.

The application of reason in determining the natural law was possible, Aquinas felt, because there was in man a natural and initial inclination to good, both in common with all creatures and as a specific adjunct of his rational nature. All men had this natural aptitude to virtuous action, but those who could achieve the necessary discipline without the help of others (and the fear of penalties) were rare, and it was this that made law necessary. The correct definition of law, said Aquinas, was that it was a rational ordering of things which concerned the common good, promulgated by whoever was charged with the care of the community. However, the prince's will, if it was to have the force of law, must be regulated by reason when it commanded.

Aquinas believed that natural law could be added to, presumably by discovery of more of the eternal law, but that its primary principles could not be subtracted from. There is one standard of truth or rightness, he asserted, known to everyone as far as the general principles of reason are concerned. As to particular conclusions of speculative reason - what is the case - there is one standard of truth, though this may not be known to all (just as a geometrical theorem is universally true even though not known to everyone); but as to particular conclusions of practical reason - what ought to be done - standards might vary. Thus the speculative conclusion that all debts should be repaid was universal, but the practical question of the repayment of a debt to be used in war against one's own country admitted of more than one answer.

"Lex injusta non est lex" wrote Aquinas, and scholars since then have argued about what he meant. A law may be unjust, he said, in any of several ways. It is unjust in respect of the end when it is not conducive to the common good but rather to the interests of the law-giver. It is unjust in respect of authority when it exceeds the legitimate powers of the person purporting to make it. And it is unjust in respect of form when it imposes burdens unequally in the community. Any such unjust law would be invalid, said Aquinas, and disobedience might then be not merely a possibility but (if the law offended against natural law) a duty. In practice, however, he recommended obedience even to unjust laws for fear of the greater evil of instability.

Aquinas thus based his theory of natural law on the eternal law of God, and this was not altogether surprising. It was not only that he was a Dominican theologian, but that he lived at a time when secular kings and princes throughout western Europe derived much of their authority from the Church and were subject to the Pope in matters of conscience. This state of affairs, in which the Church taught that feudalism was natural and therefore right, was to continue for another 250 years, and even today the Roman Catholic church claims to be the authoritative exponent of natural law.


The Renaissance and Reformation, and the collapse of the feudal system, led to greater emphasis on human liberty and on the free will of the individual, and natural law founded on the supposed will of a Christian God could less easily be accepted. Even as early as the mid-sixteenth century, writers such as Francisco de Vitoria (1485-1546) were arguing that all men, Christian or not, have equal capacity to establish their own political societies, and that the Spanish conquistadores were not justified in making war on the American Indians and seizing their property merely because they were not Christian.

Traditionally, the first seculariser of natural law doctrine is said to have been the Dutch protestant Hugo Grotius (1583-1645), who sought to justify natural law in ways that did not presuppose the existence of a wise and benevolent God. He asserted that natural law would subsist even if there were no God, and that its principles were derived from the nature of the human intellect and its desire for a peaceful society. In fact his arguments had already been anticipated by the Jesuit Robert Bellarmine (1542-1621) and others, but it was Grotius who made these ideas widely known. He is perhaps best remembered as the originator of public international law, many of whose basic principles are based on natural law ideas.

Over the next hundred years or so, various writers developed the idea of a social contract under which free men surrendered some part of their natural freedom in exchange for security. Thomas Hobbes (1588-1679) argued that before the existence of such a contract the life of man was solitary, poor, nasty, brutish and short: self-preservation was the great lesson of natural law, and in such times of war everyone had a natural right to whatever might help him to preserve his own life, even the body of another. The social contract was his attempt to improve his chances of self-preservation by cooperation with his fellows, and to this end he owed absolute unconditional obedience to the law retaining only such rights as the state chose to give him.

John Locke (1632-1704) arrived at a similar conclusion from a diametrically opposite position. To him, life before the social contract had been almost perfect, lacking only security of property. It was to remedy this defect, he said, that man renounced his natural right to perfect freedom and yielded part of his liberty to a sovereign. His consent to such a contract might be express, said Locke, but it might equally be inferred from his mere presence within the territory of the society, whereby he took advantage of its benefit. On the other hand, he said, while rulers had a right to rule they had a duty to use their power for the public good and (although he did not lay too much stress on this) could legitimately be overthrown by the people if they broke their trust.

Probably Locke's most significant contribution, however, was his belief in a right to property antedating civil society. The earth belongs to God, he said, who had given it to all men in common, but the labourer was entitled to keep the fruits of his labour. (Such reasoning implied that the ruler could not lawfully deprive men of their property by taxation without their consent.) Nevertheless, Locke (like Aquinas before him) defended the right to physical subsistence even where this undermined property rights, and was one of the first to suggest that the old, the weak and the needy might have a moral right to claim support from their fellows.

The trouble with natural law, as the Scandanavian realist Alf Ross (1899-1979) remarked, is that she is a harlot at the disposal of anyone. Monarchs and governments claimed that natural law justified their exercise of authority, while the rising middle classes used it to support their claim for private property rights. The phrase "natural rights" came to be heard more and more, and the more extreme supporters of natural rights asserted that rulers held their position on trust, and could legitimately be overthrown by the people if this trust was abused. Such a claim was heard in both the American and the French Revolutions.


The eclipse of natural law thinking in the late eighteenth and nineteenth centuries came about because of pressure from several sources. The increasing use of law as a tool of social engineering was one factor: even the early writers had recognised that natural law was neutral on some issues such as the formalities required in conveyancing, but as law came more and more to be a compromise between competing interests it became ever harder to see it in terms of moral absolutes. Meanwhile, the positivist school (whose work was discussed in the previous chapter) argued that laws were to be identified by empirically observable criteria quite independently of any moral values, and for some two hundred years their way of thinking was predominant.

A more immediate assault on natural law thinking came from David Hume (1711-1776) in his Treatise on Human Nature. Government is clearly an invention of men, he said, and the origin of most governments is known in history, so what is the basis of any claim that law is based on natural obligations? His most severe criticism, however, was levelled at the faulty logic by which natural lawyers sought to deduce "ought" from "is". The fact that a certain state of affairs is so in nature, said Hume, does not show that it ought to be so, and the whole idea that man can use reason to deduce natural law from nature is therefore unsound. (John Finnis, of whom more later, claims that man can in fact determine by rational thought what is good, without the need for any deductions from observation. Determining what ought to be, he admits, requires intelligence qualitatively different from that required for determining what is, but it is an intelligence in no way inferior to the other.)

There is a second fundamental criticism of traditional natural law teaching, in that it is quite evident to anyone who looks that actual law does not always conform with natural law: this is an argument characteristic of the positivist school. Natural lawyers reply that if positive law is all that matters, the power of the state is no different from that of a gunman: what are states without justice, asked St Augustine, but robber bands enlarged?


The revival of interest in natural law came in the immediate post-war years, when jurists throughout the western world were forced to consider the actions of the Nazi leadership in Germany during the period 1933-1945. This was no mere academic question: on the one hand the post-war German courts had to decide whether (if at all) they should apply Nazi legislation in everyday civil and criminal matters, while on the other the Allied powers had to deal with those regarded as "war criminals".

Lon Fuller is probably the leading American jurist of the mid-twentieth century, and while not wholly supporting the natural law school he criticised the positivists for their one-sided view of law as something imposed by the rulers on the governed, without any thought to its morality and purpose. In his work The Morality of Law (1964) he introduced the idea that a legal system should display a certain "internal morality", and that certain procedural requirements must be observed if good laws are to be made.

Fuller begins his analysis with a parable of an incompetent ruler called Rex, whose eight attempts to make a new code of law all fail for different reasons.

  • First, he does not make any laws at all.

  • Then he does not publicise the laws he has made.

  • Next he legislates retrospectively rather than prospectively.

  • He makes laws which are incomprehensible.

  • He makes laws which contradict one another.

  • He makes laws demanding impossible standards of conduct.

  • He changes the laws too frequently.

  • Finally, the laws he makes are not applied in practice.

A total failure in any one of these eight directions, says Fuller, results not merely in a bad legal system but in something that cannot properly be called a legal system at all. There can be no rational ground for asserting that a man is morally bound to obey a law that does not exist, or which has not been made known, or which has not yet been enacted, or which is incomprehensible, or which is contradicted by another law, or which is impossible to obey, or which is constantly being changed; and it is pointless to obey a law which is habitually disregarded by the judges. Even without total failure, there may be substantial failure in several areas, and this is the interesting case that arouses debate. In Nazi Germany, for example, there were some laws that were kept secret, retrospective legislation was common, and judicial tribunals disregarded the law when the interests of the Party demanded it. The aim of the government in such a situation is not to give the citizen rules by which to shape his conduct but rather to frighten him into impotence. But was there a legal system? Fuller felt not, but even he conceded that there is no simple test by which the citizen can assess his obligation to obey or judge the allowability of revolution.

Corresponding to each of Rex's eight modes of failure, said Fuller, there is a desirable feature of any legal system: thus laws should be made, should be published, and so on. In reality these eight standards of excellence are rarely achieved, and we are thus looking at a morality of aspiration - a target to be aimed at - rather than a morality of duty representing a minimum level that must be attained. They are not basic conditions that every legal system must fulfil, therefore, but constant pole stars guiding its progress. Fuller himself conceded that in practice not all can be achieved and some are incompatible with others: he cited the example of post-war Poland, which tried earnestly to frame its laws in language clear enough to be understood by the layman, but found this led inevitably to inconsistencies in their application by the courts. It is worth noting too that the English legal system of which we are so proud offends against the third and sixth of Fuller's principles: the common law is based on inevitably retrospective judicial legislation, while strict liability crimes and torts impose sanctions for conduct which may have been outside the defendant's control.

Fuller's "inner morality" of law thus differs from traditional natural law ideas (apart from his omission of a role for God) in that it is concerned with form rather than content. Fuller himself acknowledges this: his internal morality is complementary to an external morality which may or may not say anything about polygamy, private property, income tax or the equality of the sexes. The internal morality of law is neutral towards such questions as these, and so is not unlike judicial review, which is concerned more with the way in which decisions are made than with the substance of those decisions.

In a talk to the Association of Law Teachers in March 1999, Roger Brownsword indicated three requirements for a rational law.

First, a rational law must be formally rational and free of doctrinal contradictions; it must not contradict itself, nor must it contradict any other applicable law.

Second, a rational law must be instrumentally rational, effective in guiding people's actions and in achieving its intended purpose.

Third, a rational law must be substantially rational, based on good reasons giving it a moral legitimacy.

Brownsword does not claim that a law violating any or all of these principles is not a valid law, but he says it is not a rational law (and so, perhaps, does not deserve respect or obedience.)


The great debate between Hart and Fuller was actually initiated by the German jurist Gustav Radbruch. Radbruch had originally been a positivist, but his experience of life in Germany under the Nazis caused him to change his views, and he went so far as to say that the positivism of most members of the German legal system had been a significant contribution to the Nazis' success. A purported law is not legally valid, he said, unless it passes the system's formal tests of validity and it does not contravene basic principles of morality. A judge or lawyer should therefore denounce as invalid and irrelevant any supposed law which goes against either of these criteria, and against the second in particular.

What the lawyers and judges in Germany should have done, Radbruch argued, was treat as valid only those laws which were consistent with basic morality, and to denounce as invalid purported laws which were essentially immoral. Fuller went further, and argued that the Nazi system saw so serious a decline in the internal morality of law that a legal system as such ceased to exist during the Nazi period. He therefore suggested that the postwar courts should not recognise as valid any Nazi legislation, conceding that there might be a need for some retrospective legislation as necessary to fill any gaps.

Hart and Kelsen, two liberal positivists, disagreed with this analysis: the question for them was not "Is this purported immoral law really a valid law?" but "Is this valid law so immoral that I ought to disobey and take the consequences?" Hart gave three main reasons for his objection:

  • If only moral laws are valid, there will exist "laws" that are valid for some people - even for some judges - and not for others. Such a system would be impossible to administer fairly.

  • If immoral "laws" are regarded as invalid, people will be inclined to disregard them instead of campaigning against them.

  • A person who acts in accordance with an immoral "law" may, if the law is later declared invalid, be punished for that action and the important principle of nulla poena sine lege ignored. It would be better in the most serious cases to enact retrospective legislation expressly making the act criminal: this would make plain that the lesser of two evils was being chosen.

The differences between Hart's and Fuller's views were shown up in their debate over the case of the grudge informer. A case was reported in the Harvard Law Review in 1951 of a German woman who during the war had informed the authorities of her husband's anti-Hitler views; he was arrested and imprisoned by the Nazi courts. After the war, the wife was charged with unlawfully depriving another of his liberty under the German Criminal Code of 1871. The Provincial Appeals Court said that the sentencing judges had acted within their legal competency and so were not guilty of any crime. The wife was guilty as charged, however, because (i) she had no positive duty to inform against her husband, (ii) she had done so for purely personal motives, and (iii) she must have realised that the consequences for her husband would be contrary to the sense of justice of all decent human beings.

The Nazi statutes, added the court obiter, were highly iniquitous and imposed excessively severe penalties, but they were not a violation of natural law and so were valid laws until repealed. Unfortunately, the original Review report mistakenly said that the Court had declared the statute invalid as a violation of natural law, and it was this that prompted the debate. Hart argued that such a decision would have been undesirable - the law is the law whether it accords with natural justice or not - and that there were two better options: to let the woman go free, distasteful as this might be, or to enact an unashamedly retroactive law making her conduct criminal.

Fuller found this argument quite unacceptable, and said that if the Nazi laws were invalidated by retroactive legislation rather than by judicial decision, as Hart suggested, it merely transferred the dirty work from the judiciary to the legislature. Such a course was unnecessary in this case because the existing Criminal Code (which the Nazis had not repealed) covered the woman's conduct in any event. He questioned the exoneration of the judges, however, arguing that the Nazi statute prohibited public expressions of discontent rather than private remarks to one's wife (although in fact it had been very widely interpreted), and provided a whole range of punishments of which the judges had deliberately chosen the most severe.

There were echoes of Fuller's views in a similar case decided by the Federal Supreme Court, who said that the question of validity was to be answered in the same way for all those involved - the informant, the prosecutor, the judges, and so on. It was unnecessary to consider whether the Nazi law was invalid as contrary to natural law, however, because on the facts the original decision was clearly unjustified. The man's remarks had not been made "in public" but privately, and the judges had almost certainly erred in finding otherwise; moreover, the imposition of the maximum sentence was a violation of established principles of law requiring punishment proportionate to the offence. The judges had therefore acted unlawfully, and the woman was an accessory to their crime because her intention had been to get rid of a husband who had caught her in adultery. The woman should therefore be convicted, but the judges were acting under duress and so would not have been punished even if they had been prosecuted.

A number of jurists were uneasy on this last point, and argued that the judges could have escaped the duress by resigning. This would probably not have led to any serious consequences for themselves - not in the early days of the regime, certainly - and would have relieved their crises of conscience. However, it would have done nothing to benefit any accused persons, who would still have been tried and condemned by Nazi-appointed judges, or punished without trial by the Gestapo or SS. This apart, the reported German cases could be satisfactorily resolved on their facts, without recourse to any legislative gymnastics, but Fuller acknowledged that there might be circumstances in which the decision was less easy. He devised as a basis for discussion a problem based on the rise and fall of the mythical Purple Shirts.

The Hart-Fuller debate was not only over the punishment of the grudge informer, however: Hart and other jurists also criticised Fuller's eight principles of inner morality as being nothing of the sort. They agreed that the eight principles reflected good practice in legislation (and generally welcomed the distinction between a morality of duty and a morality of aspiration) but denied that they formed a moral basis for law. It made no more sense to speak of the principles as a "morality of law", said Hart, than to speak of a "morality of poisoning" in a collection of rules designed to ensure success in that field.

For example, Fuller and Hart differed over the South African apartheid laws, which conformed broadly with the eight principles but which were almost universally acknowledged to be immoral and contrary to natural law. Fuller drew attention to inconsistencies in the ways that different South African statutes defined race, so offending against the fourth and fifth principles, but Hart saw this as a sham: the truth, he argued, was that South Africa's laws did meet Fuller's criteria in general terms, but were designed to (and did) produce an immoral result. At best, he said, Fuller's eight principles might be necessary for a moral legal system; they were certainly not sufficient.

Conversely, said Hart, a legal system might fail substantially in several areas of Fuller's "inner morality" and yet by any normal linguistic test be a legal system working more or less effectively. It might be a very unfair and undesirable system, but that would not make it any less legal. In any case, even Fuller admitted that the Israeli "Law of Return", which promised Israeli citizenship to any immigrant Jew, was hideously obscure and almost impossible to administer, but its substantive aim was morally good and unobtainable by clear rules.

Fuller replied to such criticisms by saying that the observance of his eight principles tended to lead to good law, because evil rulers find it hard to enact evil laws in ways which do conform. Finnis added the observation that an evil government had no reason to abide by Fuller's eight principles, the last of which actually promotes inefficiency in the pursuit of its policies. Such responses are not wholly convincing, however, and leave the feeling that while Fuller's principles may well have a value of their own they do not by any means re-establish the supremacy of natural law.

Dworkin joined in the debate too, distinguishing between the "grounds" and the "force" of law: the grounds of law allow a person to predict how a judge (in Nazi Germany or anywhere else) will interpret the law and decide a case, whereas the force of law is that which creates (if it does) moral rights and duties. Unlike the strict positivists, Dworkin claimed that making moral judgements was essential in determining whether or not the community had a right or a duty to use its coercive powers, but he did not deny that an immoral legal system could exist and could create legally valid law, and he certainly did not believe that there were any objective external standards of natural law by which morality could be judged.

The debate is not really over practical results: Radbruch, Fuller and Hart agreed that the grudge informer ought to be punished, and all three tended to think that retrospective legislation was probably the best way of dealing with those who had committed "crimes" sanctioned by the immoral laws of the Nazi regime. The difference was over the way in which those "laws" should be analysed. What surely is most needed, wrote Hart, in order to make men clearsighted in confronting the official abuse of power is that they should preserve the sense that the certification of something as legally valid is not conclusive of the question of obedience. The validity of law creates a presumption in favour of a moral obligation to obey, but this presumption is rebuttable by sufficiently strong moral arguments to the contrary.

This makes a certain amount of sense, and gives meaning to campaigns for the repeal of unjust laws. If (as the extreme naturalist might say) an immoral law is not a valid law at all, what is the point in trying to change it? It is only the positivist who accepts that it is law (but who may not feel morally obliged to obey) who can sensibly devote time and effort to agitation for its repeal. Hart, one might say, is following Bentham in seeking to distinguish expositorial or analytical jurisprudence which describes what the law is, from ethical or censorial jurisprudence which considers what the law ought to be. Hart's notion of validity as independent of morality is closer to the way most ordinary people think of law - they would say that such-and-such is the law but it is immoral and so we ought to change it (or disobey it), but perhaps Radbruch is more accurate in describing the way we ought to think.


In his major work Natural Law and Natural Rights, published in 1980, the Roman Catholic scholar John Finnis sought to restore the credibility of natural law. He denied that natural law depended on the deduction of moral principles from observation (so answering Hume's major criticism), and denied too that legislation offending against natural law was necessarily invalid. Natural law, he said, consists of the set of principles of practical reasonableness - that is, reasonableness in deciding and acting - essential to the ordering of human life and the human community.

It is often supposed, wrote Finnis, that an evaluation of law as a type of social institution must be preceded by a value-free description and analysis of that institution as it exists in fact. But the development of modern jurisprudence suggests that a theorist cannot give a theoretical description unless he also participates in the work of evaluation. Actions and practices can be fully understood only by understanding their objectives as conceived by those who performed them. Finnis therefore began his argument by asserting that there are seven basic human "goods" which are self-evident.

These seven basic goods, which every reasonable person must accept as valuable objects of human striving, are:

  • life, including good health and freedom from pain; the procreation of children may also be included;

  • knowledge of what is true, for its own sake;

  • play, or any activity enjoyed purely for its own sake;

  • aesthetic experience and the appreciation of beauty;

  • sociability & friendship, and acting in another's interest;

  • practical reasonableness, being able to bring one's intelligence to bear in choosing one's actions; and

  • religion in its widest sense.

The justification of these as basic goods depends on assertion. It is obvious, said Finnis, that a man who is well-informed simply is better-off (other things being equal) than a man who is muddled, deluded and ignorant ... whether I like it or not, so knowledge is indeed a self-evident good and not a subjective preference. The other basic goods are similarly justified. All other forms of good, said Finnis, are no more than ways of pursuing one or more of these. None of the basic goods is more important than the others, although individuals may choose from time to time to give preference to one rather than another in planning their lives. But this analysis is open to challenge. Are the seven basic goods really self-evident beyond any possibility of doubt? Is knowledge always a good, for example, or is it better that men should remain ignorant of certain things? Is friendship something to be valued for its own sake, or merely for what it achieves in terms of mutual benefit? Should other basic goods have been included, such as power or physical pleasure, which are seen by some as ends in themselves? Are not play and aesthetic experience simply two manifestations of physical pleasure? Is religion any more than a facet of knowledge?

Undaunted, Finnis added to the basic goods certain "basic methodological requirements" which together go to constitute the universal and unchanging principles of natural law and so enable us to have objective knowledge of morality. These requirements are:


It is unreasonable to live life from moment to moment without a plan (but contrast Matthew 6.24).


"Arbitrary" seems to mean any view opposed to that of Finnis, who says for example that although a scholar may have little taste or capacity for friendship, it is stupid and arbitrary to speak as if this were not a real form of good.


There is reasonable scope for self-preference but not for selfishness. In particular, one must apply the same moral standards to oneself as to others.


On the one hand, the individual should avoid any single-minded fanaticism that might exclude all other considerations, but on the other a commitment once made should not be lightly abandoned and reasonable efforts should be made to find ways of carrying it out.


One should try to bring about good (and avoid harm) by actions that are efficient for that purpose. Where some harm is unavoidable, it is reasonable to prefer human good to that of animals, the preservation of life to that of property, and a

lesser to a greater injury.


The end does not justify the means, and an act which itself does only harm to some basic good must be avoided even though its foreseen ultimate consequences might be beneficial. This is controversial, but would justify (for example) Catholic teaching on abortion.


This cannot be a purely arithmetical calculation, as utilitarianism might suggest, but must involve something less well defined.


An act which one instinctively feels or thinks wrong is to be avoided, even though one's judgement may be mistaken.

Since the basic goods and the methodological requirements are self-evident, Finnis asserts, they may be used as axioms from which further "oughts" can be deduced by valid reasoning without the is-to-ought leap so strongly criticised by Hume. It is true that such a logical fallacy is avoided, but the logically valid conclusions are not necessarily true unless we accept the truth of the premises - the basic goods and methodological requirements - from which they are derived!

Practical reasonableness requires a well-organised society, because only in communal life can man maximise his potential. Such a society in turn requires a legal system to enforce and amend the common code of behaviour: law is thus a means to the common good, fulfilling the requirement of practical reasonableness. This is not to say that human rights are necessarily subject to the common good, as utilitarians would argue: on the contrary, says Finnis, some human rights (such as freedom from torture) are absolute. But is a society really necessary for the achievement of the basic goods? Can a man not pursue all these ends living in isolation with his family? Even given such a society, is there any obligation on an individual to contribute to the common good?


The continued academic interest in natural law rests on an attempt to find a rational basis for intuitive morality, but the common law systems, including that of English law, have made little room for natural law in general. In England, Sir William Blackstone (1723-1780) began his Commentaries with an assertion of the classical natural law position that human laws derive their authority only from God's superior law, and are invalid if they run contrary to the laws of God, but ignored this assertion almost entirely in his exposition of English law as it was practised. There was once a limited amount of truth in his opening assertion even in English law.

Bonham's Case (1610) 77 ER 646, Coke CJ

P was fined and imprisoned by the President and Censors of the College of Physicians, acting under a statute of Mary's reign, for practising medicine without a licence. Quashing the penalties, Coke CJ said the law could not countenance the same people acting as prosecutors and judges, particularly when they would get to keep the fine paid. Obiter, when an Act of Parliament is against common right or reason, or repugnant, or impossible to be performed, the common law will control it and judge it void.

Appeals to natural law ceased to have any practical effect in English courts, however, once the doctrine of Parliamentary sovereignty was recognised in the early eighteenth century. Nowadays there is little or no scope for any such appeal except in the limited field of judicial review of subordinate legislation. This may now be changing again under the growing influence of European Community Law as the European Court of Justice applies Continental legal thinking and more recently the provisions of the European Convention on Human Rights to the cases before it, but there is a long way yet to go.

Liversidge v Anderson [1941] 3 All ER 338, HL

The Home Secretary D had powers under wartime legislation to intern anyone whom he had reasonable cause to believe to be sympathetic to the enemy, and P was detained by an exercise of this power. The House of Lords (Lord Atkin dissenting) said it could not enquire as to D's grounds for his belief: in effect, "if he has reasonable cause ..." meant "if he thinks he has reasonable cause ...", and the decision could not be challenged except for bad faith.

Corbett v Corbett [1970] 2 All ER 33, Ormrod J

A man P sought an annulment of his marriage to R, who (as P knew at the time of the ceremony) had been born male but had undergone a sex-change operation. Granting the decree, the judge said such a marriage must always be a nullity. It could never lead to the natural consequences of marriage - one must assume he was thinking of procreation, though he did not make this clear - and so could not be lawful.

Bennett v Bennett [1952] 1 All ER 413, CA

Following a divorce, a wife sought to enforce the husband's agreement to pay certain maintenance in return for the wife's promise not to continue a court action. The Court of Appeal, dismissing an appeal from Devlin J, said such an agreement was contrary to public policy. Denning LJ said covenants in restraint of trade were not "illegal" in the sense that a contract to do a prohibited or immoral act is illegal, nor merely "unenforceable" in the sense that a contract within the Statute of Frauds may be unenforceable for want of writing; rather, they lay somewhere between.

Sweet v Parsley [1969] 1 All ER 347, HL

A schoolteacher A was convicted of "being concerned in the management of premises used for drug taking" when students living in a cottage owned by her (but which she visited rarely) were found to be smoking cannabis. The House of Lords, reversing the Divisional Court, said this offence required mens rea in the form of some knowledge. Lord Reid said that while the courts might readily construe a statute as imposing strict liability where it was concerned with acts that were not criminal in any real sense but which in the public interest were prohibited under a penalty, they should be very reluctant to do so where acts of a "truly criminal" character were involved.

Oppenheimer v Cattermole [1975] 1 All ER 538, HL

P was a German Jew who had come to England in 1939 to escape Nazi persecution, and who had become naturalised in 1948; a tax case turned on his nationality at particular times. The House of Lords said P had lost his German citizenship under a German law of 1913 when he became a British citizen, but declined to apply a Nazi decree of 1941 by which all Jews living abroad were deprived of citizenship. Lord Cross, speaking for the majority, said that while there were many examples of legislation which might now be thought unjust, the barbarity of much of the Nazi legislation was unique. He had no doubt that on grounds of public policy the courts should refuse to recognise this decree, and later in his speech he referred to "an enactment which is so great an offence against human rights that it ought not to be recognised by any civilised system of law".

The language chosen by Lord Cross highlights the increasing attention now being paid to "natural rights", or "human rights" as they have come to be called. Many governments, particularly those of the developed world, have subscribed one or more of the declarations of human rights produced in the last fifty years, and even those who (like HMG) do not make the terms of such declarations an overriding part of municipal law normally attach great moral force to what they say.

P v S [1996] All ER (EC) 397, ICR 795, Times 7/5/96, ECJ

A senior employee at Cornwall College was dismissed after informing his employers that he was to undergo "gender reassignment" (a period of cross-dressing followed by surgery) to become female. On a reference by the Industrial Tribunal, the Court of Justice said the 1976 Directive could not be confined solely to discrimination arising from a person's sex as such, but extended to discrimination of the sort practised here. As the Court had repeatedly held, the right not to be discriminated against on grounds of sex is one of the fundamental human rights whose observance the Court has a duty to ensure.


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