In the preface of The Concept of Law, Hart wrote “that the aim of this book has been to further the understanding of law, coercion, and morality as different but related social phenomena”. In this paper however, I would be focusing only on Hart’s views of the relationship between law and morality and support my opinion in agreement or disagreement with several other views in this area. 
Hart’s general account of law is not to evaluate or justify on moral or other grounds  : he is involved in analytical jurisprudence and descriptive sociology where his central assignment is to recognize the nature of a legal system at anywhere and any time in history.  As a positivist, he treats law as morally neutral.  Could something so nasty that there could be no moral justification be valid law? Could provisions that promote discrimination be valid law? Hart provided the answer yes. 
Thus, the main issue of this paper would be whether Hart’s account on law and morality survive other opinions’ attack.
Hart’s most prominent critic, Dworkin 
Dworkin criticized Hart based on two issues: rights and duties and the identification of the law. In relation to rights and duties, Dworkin holds the view “that there must be prima-facie moral grounds for assertions of the existence of legal rights and duties” and that “legal rights must be understood as a species of moral rights”  while Hart maintains that there could be legal rights and duties that have no moral justification whatsoever due to their supreme importance to human beings. 
With regards to the identification of the law, Hart concedes that laws may be identified without any reference to morality.  So long as rules are accepted and enforced by authorities, those rules are valid law.  Dworkin however, drew a distinction between interpretive and preinterpretive law  : there are possibilities of existence of evil legal systems without moral justifications but when this is so, we may resort to “internal skepticism” and deny such systems as laws. 
Hart replies to this: “aˆ¦the distinction between interpretive and preinterpretive law concedes rather than weakens the positivist’s caseaˆ¦in a descriptive jurisprudence the law may be identified without reference to morality…Dworkin’s message gives no reason for the positivist to abandon his descriptive enterprise, nor is it intended to do soaˆ¦for the law may be so evil that ‘internal skepticism’ is in order, in which case the interpretation of the law involves no moral judgment and the interpretation as Dworkin understands it must be given up.” 
Natural lawyers now claim: “contemporary voices tell us we must recognize something obscured by the legal “positivists” whose day is now overaˆ¦there is a ‘point of intersection between law and morals’aˆ¦” 
This is the sharpest distinction between Hart and natural lawyers. The Thomist classical explanation of natural law is said to be of twofold contention: existence of principles of true morality or justice, discoverable by human reason without aid of revelation although they have a divine origin and that man made laws which conflict with these principles are not valid law.  If this is correct, Hart’s famous essay Positivism and the Separation of Law and Morals would be bizarre.
Taking Finnis’s view (as he expressed natural law in fresh terms) as example, running in parallel with the Thomist’s tradition but more elaborately worked out,  he considers that natural law theory need not be of the view that unjust laws are not law but believes that sound laws are to be derived from their principles gain from the force of reasonableness and not circumstances.  He does not consider the validity of unjust laws as an important matter, rather concludes that a ruler’s authority to make laws rests on the needs of the common good and if his authority is applied against this, then his laws lack the authority they would otherwise have and thus creates no obligation to obey them, so might render ineffective the just parts of the legal system.  The ruler is still under an obligation to repeal those unjust laws. 
If we turn to consider Hart’s view, we may see that his is rather different. In the chapter of Laws and Morals,  Hart speaks about the issue of natural law and legal positivism where he identifies legal positivism with “the simple contention that it is no sense a necessary truth that laws reproduce or satisfy certain demands of morality, though in fact they have often done so.”  Although from this we could see that Hart has no reason deny the influence of morality in the content of law, but legal validity of a rule is dependent on the rule’s derivability from some basic conventional criterion of legal validity accepted in a particular legal system.  Hence, “the mere fact that a rule is just or reasonable will not make it a law; nor does the injustice of a rule demonstrate that it is not a law.”  Even if law and morals are closely bound up in a system, it will always be possible to separate them in some conceivable legal system. 
Law would still be valid even if it is morally heinous; it is not an issue of the intention of private citizens in accepting the law.  Hart would ask: “Is is worth going through punishments and coercion due to disobedience just because a law is evil in the eyes of morality?” Even if the answer to this question is yes and leads to a corrupted and failed legal system does not mean that the legal system has never existed or has never been valid. 
The minimum content of natural law
Although Hart does agree with Austin’s formulated doctrine that “the existence of law is one thing; its merit or demerit is another”  (the separability thesis) which has been claimed to be false by the traditional natural law doctrine because moral considerations form a necessary condition of legal validity  , Hart also talked about something called the “minimum content of natural law” or in other words as we call him “the soft positivist”. He tells us: “theories that approach law in purely formal terms, without reference to specific content or social needs” have been proved to be inadequate. 
There is a high concurrence in rules of which a legal system contains where there are rules prohibiting or regulating acts of human behaviour and daily transactions.  It is not coincidence that a legal system contains these rules but they are “dictated by fundamental features of human nature and circumstance that they are said to be necessary”.  They are “natural necessities”.  It may then be the case that every legal system, immoral and evil it may be, would have to have some morally acceptable content, promoting some moral goods. 
On the surface, we might find that Hart’s argument seems to be rather similar to arguments of natural lawyers such as that of Finnis. Hart justifies the existence of his minimum content of natural law with the term of the value of “survival”, although minimal, it is presupposed to be our inquiry to law because our concern is with continued existence and that as we live in a “world with each other”, we understand the general value of survival.  We might relate this value with the status of an objective good, as Finnis seeks to demonstrate that this good is presupposed by our practical reasoning, providing us with “intellectual access to the world of human life and action”. 
Hart’s view on the other hand would most probably be criticized by hard positivist such as Austin, Kelsen and Bentham. Both Bentham and Austin insisted the need to distinguish with maximum clarity that, law as it is from law as it ought to be.  Bentham insisted on this distinction by reference to principles of utility only without characterizing morality.  Kelsen on the other hand had also insists that validity of the law has in no way concerned with its content but the law (a norm for Kelsen) is valid due to its creation in certain way.  His theory of “double purity” has been so pure that he ignored alien elements such as sociology and morality from the question of legal validity. 
Hart’s reply to Bentham and Austin might be that it is not because there is no distinction between what law is and what it ought to be but the word “ought” reflects some standard of criticism and one of these is a moral standard, not all of them.  In relation to Kelsen’s approach, he describes it as “purchasing analytical uniformity at the price of distorting the law’s diverse social functions” and that his purely formal analysis of the structure of the law obscures the difference between “a law imposing a tax and a law creating a crime with a financial penalty”. 
Lon L. Fuller, a natural lawyer or a positivist?
Most readers of The Concept of Law might be in agreement with Fuller when he says: “I must confess when I first encountered the thoughts of Professor Hart’s essay, his argument seemed to me to suffer from a deep inner contradiction…At times he seemed to be saying that the distinction between law and morality is something that exists, and will continue to exists…other times, he seemed to be warning us that the reality of the distinction is itself in danger and if we do not mend our ways of thinking and talking we may lose a ‘precious moral ideal’, that of fidelity to law.” 
Fuller thinks that when Hart speaks of morality, he seems to have in mind all sorts of legal notions about “what ought to be”, without regards to their “sources, pretensions and intrinsic worth”. He seems to assume that nasty aims have as much coherence as good ones.  Fuller refuses to accept this assumption and claims that coherence and goodness have more affinity than coherence and evil. Thus when men are compelled to justify their actions, the effect would be to pull those decisions towards goodness. 
Fuller talked about external and internal morality as requirements in order for something to be called law as law itself is powerless in bringing this morality into existence.  The external sense is that the authority that makes law must be supported by moral attitudes while the internal sense is that the monarch has to accept the internal morality of law itself.  Fuller concentrates on his concept of “inner morality of law” that a legal system should provide for coherence, logic and order in order to command the fidelity of a right-thinking person.  A legal system that lacks this “inner morality of law” cannot constitute a legal system.  This theory however seems to be completely neglected by Hart although he made brief mention to the “justice in the administration of the law” but dismisses it quickly as being irrelevant to his main work. 
What then happens to Fuller’s “fidelity of law” if some people, such as petty criminals or revolutionaries do not have feelings to this kind of fidelity?  “People who claim that a posited law is not valid because it fails to meet certain external criteria muddy the water” says Hart.  Hart argues that although Fuller’s point would help in providing a separation between “ends” (in working non-rationally only) and “means” (discussion of rational arguments), but the relevance of his argument has little to do with the separation between law and morals.  However, if we are to consider all evil things as not law, it would raise a bulk of philosophical issues before it could be accepted as valid law.  This would be troublesome because the right way to criticise the law should be by facing reality and not only base it on propositions of philosophy. 
Moreover, in order for there to be a fusion between is and ought, two criteria must be fulfilled: “ought” need not have to do with morals and that most importantly, it is only exceptional that “one way of deciding a case is imposed upon us as the only natural or rational elaboration of some rule…for most cases of interpretation, the language of choice between alternatives, ‘judicial legislation’ or even ‘fiat’…better conveys the realities of the situation.” 
It is on the other hand, truly a paradox of the Hart-Fuller debate that both actually agree on the matter of deciding “grudge informers” cases after the Nazi era that retroactive statute should be the answer although their reasons differ from each other.  Fuller was of the opinion that “…a statute as a way of symbolizing a sharp break with the past…isolating a kind of cleanup operation from the normal functioning of the judicial process…would become possible for the judiciary to return more rapidly to a condition in which the demands of legal morality could be given proper respect.”  To a natural lawyer, laws that are in conflict with higher codes than decrees of man-made are void, while laws (for Fuller), as long as they fulfil the requirements of his inner morality of law would presumably be valid. In this case, Fuller poise as a positivist yet the tinge of natural law surrounds him. 
Where then does Hart’s concept stand? Although to the end of his life, Hart remained acknowledged about the possibility of similar objectivity in matters of morality, but he holds that one can be reasonably certain about law even when morality is being open to argument.  Dworkin’s theory on the other hand seems to be illustrating in between positivism and natural law but it should be reminded that natural and positivism are best looked as independent views for different issues.  Neither Hart nor Dworkin wins this debate because they have been talking past each other, both about separate things. 
Next is the confusion between the opinion of natural lawyers and Hart as Hart would agree with the classical natural theory where he does not think that “positive laws that are contrary to justice should be obeyed as a matter of conscience.  Although this is so, Hart would still not qualify as a natural lawyer because he is against the compulsion that human law has to be subordinated to natural law.  However, natural lawyers, such as Finnis would think that Hart is confused or even misunderstood the classical theory and that albeit Hart has presented himself as a supporter of legal positivism, he is aware that there is a fragment of truth in natural law thinking which he had attempted to single out. 
On account of the “minimum content of natural law”, Epstein is of the opinion that “the function of any legal order is not just to minimize the risks to survival, but to maximize some overall measure of social happiness or welfare” to which is far wider and complete than Hart knew about it.  He thinks that Hart’s theory should instead be “The not so minimum content of natural law”. 
On his debate with Fuller, Hart uses his “minimum content” theory again to balance the perpetual tension between legal positivism and natural law.  If the question before us is what counts as valid law, Hart would have in one sense won the debate. “Whether a given proposition would count as law is not decided solely by parsing its text to determine its meaning or moral worth…content and form are quite beside the point. There is no method of visual or analytical inspection that separates those law-like statements that count as law from those statements that are bills that have yet to be enacted…for the grand jurisprudential inquiry, institutional variations between countries do not matter”. 
In my opinion, I would agree with Hart on his concept of law and morality. Absolute separation of law and morality does not exist. Man-made laws that are good in the eyes of morality do not come into existence by coincidence because by nature, men do apply morality in their daily walk of life.  Despite this fact, Hart is telling us that in any legal system “law is” and this should be true because he is talking about the validity of the law and the existence of a legal system. Even if the law fails to be what it “ought” to be, we could not deny its existence.