The practice of differentiation is an integral part of precedent-based legal reasoning. The distinction presupposes that a precedent is not followed, even if the facts of the subsequent case fall within the scope of the relationship of the earlier case. Since the subsequent case falls within the scope of the prior relationship (i.e. the scope of the rule), one would expect the decision in the subsequent case to be the same (unless the court has the power and decides to set aside the earlier case). However, in legal arguments based on case law, the subsequent court is free not to follow the earlier case by pointing out a difference in facts between the two cases, even if those facts are not included in the relationship of the earlier case. A precedent is a principle or rule established in a previous court case that is binding or persuasive, without the need to go to court for a court or other court when deciding subsequent cases involving similar questions or facts.    Common law systems place great importance on deciding cases according to consistent rules of principle so that similar facts lead to similar and predictable results, and adherence to precedent is the mechanism by which this objective is achieved. The principle that judges are bound by precedent is known as stare decisis (a Latin phrase with the literal meaning of “to stand in the things that have been decided”). The common law precedent is a third type of law, equal to statutory law (i.e. laws and codes promulgated by legislative bodies) and subordinate laws (i.e.
regulations issued by law enforcement agencies in the form of delegated laws) – in British parlance – or regulatory law (in American parlance). The foregoing arguments and analogies are two central forms of reasoning found in many legal systems, particularly common law systems such as those of England and the United States. A precedent means that a previous decision is followed in a later case because the two cases are the same. The analogy implies that an earlier decision is followed in a later case because the subsequent case is similar to the previous one. The main philosophical problems raised by precedents and analogies are: 1) When are two cases “equal” for the purposes of case law? 2. When are two cases “similar” for the purposes of the analogy? and (3) In both cases, why should the decision in the previous case affect the decision in the subsequent case? The analogies, like the previous ones, arise in a doctrinal context. This case raises a question of law, for example: does the impersonation of a friend interfere with the victim`s consent in the rape law, is it cross-writing “speech” in the First Amendment of the United States Constitution, does the defense of coercion require that the accused acted as a reasonable person would have done? Other cases involving the validity of consent or the scope of protected “speech” or the adequacy of the defence offer possible analogies. An analogy may be either with another case or with another legal doctrine, and the analogy is based on the fact that there is a common characterization of the facts in both cases or of both doctrines relevant to the issue. Thus, knives can be analogous to weapons if the problem is with weapons, but knives can also be analogous to teaspoons if the problem is with cutlery.
Coercion may be analogous to provocation when it comes to defence, but coercion may also be analogous to incitement to complicity. Two doctrines or sets of facts are not analogous abstract, but in the context of a legal question.  One issue that may arise with respect to precedent is why it is justified for court decisions to be treated in this way in the first place, that is, to help make the law. However, there is a more specific question. At least at common law, the doctrine of stare decisis requires subsequent courts to follow previous decisions, even if they were wrongly decided. To say that a case has been “ill-decided” means that, given the law, the legally admissible grounds relevant to the case do not support the court`s conclusion. It should be emphasized that such a conclusion depends on the context provided by the existing legal doctrine. Consider the question of whether parents should be able to cover the cost of raising a healthy child if it is born as a result of negligent sterilization by a parent. In some jurisdictions, these costs are recoverable, in others they are not. Here, it is quite possible that these contradictory decisions are both correct, in the sense that each is correct in its own doctrinal context.
The question of whether a decision is erroneous is therefore not a question of how the case is to be decided without reference to the law, but whether it contradicts the merits of the legally relevant reasons. Justice McHugh of the High Court of Australia in relation to precedents in Perre v Apand: Stare decisis reduces the number and scope of legal issues that the court must resolve in litigation. It is therefore a time saver for judges and litigants. Once a court clarifies a particular point of law, it has set a precedent. Thanks to stare decisis, claims can be rejected quickly and efficiently, as disputes can be resolved using rules and principles that have been established previously. Stare decisis can therefore encourage parties to settle cases amicably, thereby increasing the efficiency of the judicial system.  The fundamental problem with this reasoning in the case of precedents is that it suffers from a kind of circularity. It is true that legal systems that follow precedents give rise to hopes that previous decisions will be followed in the future. However, it is important to remember that only legitimate expectations should be considered when making decisions, not just the expectations that someone is having. The mere fact that a decision has been taken in the past does not in itself give reason to believe that it will be followed in the future and certainly does not give rise to any claim that it will be followed.
The fact that a company orders stationery from a supplier at the beginning of the year may raise hope, and perhaps even expectation, that it will do so again later in the year, but the supplier has no “legitimate” expectation that it will do so, and the company does not set a precedent for itself. If, on the other hand, there is an institutional practice of following previous decisions, the confidence of those subject to future decisions may give rise to legitimate expectations, but the institution is always free to announce that it will no longer consider previous decisions binding and will instead decide on the merits of each case. Similarly, it is common in some institutional bodies for decisions of the past to be followed so that a decision is taken provided that it “does not set a precedent” for the future. However, the strongest justification for analogical thinking lies in the value of reproducibility. This is often framed in terms of the importance of “consistency” in law (MacCormick 1978, 153, 187-8; Sunstein, 1993, pp. 778-9; see also Raz 1979, 204–6 on “partial reform”). Arguments for coherence generally emphasize their instrumental value.  This is linked to the reproducibility of judicial decisions. There are two important features of legal decision-making. The first is the fragmentary nature of the legal material. The second is the plurality of decision-making bodies.
Legal documents – precedents, laws, conventions, principles – are fragmentary in two ways: (a) they are the work of many different hands at different times and with different points of view, and (b) different areas of law owe more to some hands and at certain times than to others. As a result, legal doctrine tends to show only weak overall coherence, whereas it may possess thick local coherence. The pluralism of decision-makers is also twofold: (a) there are many people who make decisions using the same materials, and (b) these people do not share a unified evaluation perspective. Given the fragmented nature of the legal material and the plurality of decision-makers, there is considerable scope for disagreement when decision-makers are faced with new issues. A persuasive precedent (also a power of persuasion) is a precedent or other legal document that is not an enforceable precedent, but is useful or relevant and can guide the judge in deciding an ongoing case. Compelling precedents include cases decided by lower courts, even or superior courts in other geographic jurisdictions, cases brought in other parallel systems (e.g., military courts, administrative tribunals, indigenous/tribal courts, state vs. federal courts in the United States), statements in dicta, treaties, or academic law journals, and in certain exceptional circumstances. Case of other nations. Treaties, bodies of universal law, etc.
Precedents assume that decision-makers can properly determine the merits of cases pending before them, but the law naturally operates under less than ideal conditions when decision-makers make mistakes and disagree among themselves on the merits of cases. In practice, the outcome of a case may be uncertain, not only because the correct outcome is rationally indeterminate, but also because decision-makers are fallible. In this context, it can be argued that jurisprudential practice has a number of advantages, as it can make institutional decisions reproducible (see Eisenberg 1988, 10-12, 23-4, of which it is invented; and Schauer 1987, 597-8). The fact that a decision can be replicated refers to the fact that it is possible for others to make an informed judgment about the likelihood of a particular outcome, taking into account relevant legal documents, the canons of reasoning used in a system, and the knowledge of the general culture from which decision-makers come.