The nature of our legal system has become so ingrained in our everyday thinking that we typically forget that other types of systems exist. How often have we heard (or even been heard to say) some reference to Marbury v. Madison, Brown v. Board of Education, Roe v. Wade, or Edgewood v. Kirby?
These and other cases are cited often by the media, politicians, lawyers, activists and concerned citizens because they form a fundamental component of the body of law in both the Texas state legal system and on the federal level as well.
The dominant type of legal system in the United States - and many former British colonies - is the common law system. This system, according to received wisdom, developed somewhat inadvertently as the result of the practice in England of sending itinerant judges around to various villages to try pending cases.
Legislatures and other professional law making bodies as we know them now did not exist many centuries ago; nor did the printing press. In short, the government apparatus for producing law and the physical machinery for making it available in print did not exist. Consequently, judges usually relied on general knowledge of the law, their own innate reasoning abilities, and their knowledge of similar prior cases that they had adjudicated. Judges would match up the facts of the case at hand with preceding cases, and make rulings accordingly.
This process helped provide some consistency in adjudication (in the absence of any other higher authority), plus adaptability to local circumstances, as well as flexibility over time.
Common law is most often compared to the continental system, another type of system that prevails today in much of Europe and parts of the Americas. This system has its roots in Roman law and the Napoleonic code formulated in France under, well, Napoleon. In continental systems the law is quite detailed and legal reasoning is almost exclusively derived from the law and other written codes.
Common law systems also derive legal reasoning from written laws and codes, but they accord considerable sway to the rulings and the reasoning of preceding legal cases, also known as precedents or case law.