What is a court case but the opinion of a Judge? Citing previous judges opinions has somehow become significant in law nowadays, but it still boils down to the opinion of a Judge.
The English common law system does not exist without judicial opinions being significant. That goes back about a thousand years.
A case is a legal dispute or controversy, and the Opinion sets forth the issues, applicable law, and the decision of the case. The courts are constitutionally empowered to state what the law is. The precedential holdings of the higher court are binding on subordinate courts, but not themselves.
The United States uses the common law system of law. Every State but Louisiana uses the common law system.
Black's Law Dictionary, 11th Ed.
common law. The body of law derived from judicial decisions, rather than from statutes or constitutions, Caselaw.[...]
American common law. (1813) 1. The body of English law that was adopted as the law of the American colonies and supplemented with local enactments and judgments. (2) The body of judge-made law that developed during and after the United States' colonial period, esp. since independence.
[...]
4. The body of law deriving from the law courts as opposed to those sitting in equity. ... The common law of England was one of the three main historical sources of English law. The other two were legislation and equity. The common law evolved from custom and was the body of law created by and administered by the king's courts.
Without court opinions and judicial precedents, the common law system cannot exist.
From the cited Digest of Select British Statutes, preface at XVI,
The report which they have submitted, is, doubtless, entitled to high respect and consideration, as containing the opinions of men who rank in the highest grade of the profession, and in the public confidence, but it ought to be carefully distinguished from a JUDICIAL DECISION; of the character of which it does not partake.The distinguished characters who have made the report, it is confidently presumed, would not wish that it should be so considered; but on the contrary, that whenever the question comes judicially before them, whether a particular English statute, or any part of it, is or is not in force in Pennsylvania, they will hear without prejudice, whatever may be urged on either side; and without otherwise adverting to the circumstance whether such statute be comprised in the report or not, will be solicitous only to form a correct decision.
The opinion of the superior court, in any state, determines the law, in relation to questions judicially decided. Stare decisis is a maxim, in adhering to which the public tranquillity is deeply interested. It being, in a certain degree, less important what the law is, than that it should be ascertained and known. In respect to ascertaining the law, the judiciary have an arduous and sacred duty to fulfil. In the discharge of which every Judge must feel the high responsibility which rests upon him. He must be sensible of the necessity of viewing the subject in all its bearings; and to enable him to do so must be anxious to hear the arguments of learned counsel, on both sides of the question; and that his opinion should be the result of careful research, and due reflection.
Such are the opinions which ought to ascertain the law: and a point thus settled should not be the subject of future litigation or argument.
Dare I say that this is argumentum ad antiquitatum?
I've read quite a bit of "natural law" from the 1700s, and the common thinking of the natural law philosophers is that the laws of nature and of nature's God can be discovered by clear thinking and some foundational principles.
Like mathematicians with their proofs, the natural law philosophers tend to start out with some basic principles, and derive further insight into natural law by the use of reason.
That something has always been done that way before does not enter into their thinking.
That decisions are seldom derived from "first principles" is one thing that I have always seen as a flaw in our legal system.
The reason I see it as a flaw is because if any precedent has an error in it, that error translates into subsequent errors for any decisions using it as precedent.
Plessy vs Ferguson comes to mind.