The recently completed United States Supreme Court term has generated a gread deal of internet comment and analysis. Websites such as the Volokh Conspiracy are loaded with critiques and discussions as to what the various opinions mean and argue over the legal principles that are either vindicated or violated by these decisions.
What is interesting about these discussions is that very smart people disagree sharply over the legal principles, interpretations and construction of the law. They also argue over history and legal philosophy, supporting wildly varying conclusions. In reading these discussions, one can make the following observations:
There are a number of philosphies of law, each of which presupposes the existence of some definite thing, such as a divine law giver, a state of nature, a social compact, or natural order. The position taken in these abstract legal arguments depends largely on what one presupposes as the foundation of law. TO understand the arguments, it might be helpful to fully understand the different theories by reading Aristotle's Rhetoric or Montesquieu's The Spirit of Laws or Thomas Aquinas's Summa Theologica, but in understanding how the controversies in law arise, it is helpful to presume, not a particular fundamental principle, such as the social contract, but merely to accept that legal reasoning presumes such a principle, regardless of what that is.
Legal reasoning tends to be fairly consistent: specific observations and historical data are analyzed to try, using inductive reasoning, to identify the underlying principle that will resolve the dispute. Deductive reasoning then applies this principle to the specific facts to the case at issue. This is true whether one is an originalist or legal positivist or utilitarian, or whatever. This process is subject to the limitations and quirks of human cognition. Very smart people reach different conclusions based on the same data becase the cognitive processes that are used are not deterministic.
When a person analyzes facts and data and legal precedent, and uses them to distill an underlying legal principle, he is using the cognitive process of pattern recognition. This process has a sensitivity and specificity associated with it. Someone who is very adept at recognizing recurrent patterns and readily identify the common principle in disparate facts is also likely to find patterns where none exist. This is a natural consequence of pattern recognition in human cognitive processes and is responsible for the phenomenon of apophenia, the experience of seeing patterns in random data. This potential lsource of "false-positive" error affects not only legal reasoning, but all forms of cognitive analysis where pattern recognition is necessary, such as interpreting electrocardiograms. In order to increase the liklihood that a doctor will correctly identify the subtle patterns associated with particular types of cardiac pathology, he will have to accept the risk of identifying that pathology when none is actually there. He trades off false positive interpratations as the price of minimizing false negatives.
In the legal context, this apophenia phenomenon leads legal scholars on jurists to find patterns in factual scenarios, legal precedents and modern culture that appears to fit with a certain principle. Sometimes they derive a useful rule or concept, but they also will occasionally be fooled into thinking that they have identified an underlying truth that really isn't there.