Half a dozen obvious propositions

The English common law consists of about half a dozen obvious propositions, but unfortunately nobody knows what they are. 

Why does this aphorism, which I've just stumbled on, tickle me? It's known to us through Harold Chaloner Dowdall (1868-1955), a high court judge. Whilst he didn't invent it, he was sufficiently impressed by it to record it for posterity in the following letter to The Times in 1932, relating a remark he heard many years earlier when a junior barrister. 

Lord Sterndale [another high court judge] once said, “The common law consists of about half a dozen obvious propositions, but unfortunately nobody knows what they are.” He was reading a case I had looked up for him, and I did not know whether he was speaking to himself or enlightening a junior barrister in the mysteries of the law, and as his clerk immediately called him into Court the matter dropped. He was a leader at the time, and I think it was not long after he had taken silk. The observation is so witty and true that, unless it is already familiar, it deserves record; but as the number of those who knew Lord Sterndale diminishes, it would be interesting if any of your readers ever heard him make a similar observation.

The clerk immediately calling Lord Sterndale into court puts one in mind of the person from Porlock. Harold Chaloner Dowdall besides being a judge was also a regular commentator on ecclesiastical affairs, and in 1908-9 served as lord mayor of his native Liverpool. 

The phrase “taken silk” referred to a barrister becoming a Senior Counsel. I know all this from the Quote Investigator, who has additional information with citations if you want it.