Forearmed with knowledge
In the 19th Century, a new pseudo-science emerged to join the likes of alchemy and astrology. Called Phrenology, it claimed to be able to judge the aptitudes and characteristics of people by noting the bumps on their head, which presumably would give clues to the structure of the brain within the skull. The most important of these Phrenologists was a man named Fowler.
From the Skeptical Inquirer:
Forearmed with a knowledge both of phrenology and the tricks of con artists, the famous author Mark Twain performed a simple single-blind reliability test. In 1872 or 1873, he visited Fowler's London office and paid for a reading using a pseudonym.
"he found a cavity, in one place; a cavity where a bump would have been in anyone else's skull. That cavity, he said was all alone, all by itself, occupying a solitude, and had no opposing bump, however slight in elevation, to modify and ameliorate its perfect completeness and isolation. He startled me by saying that that cavity represented the total absence of the sense of humor!"
Twain returned to Fowler three months later and sat for a second reading, this time identifying himself. On this occasion, the reading differed greatly: "Once more he made a striking discovery-the cavity was gone, and in its place was a Mount Everest-figuratively speaking-31,000 feet high, the loftiest bump of humor he had ever encountered in his life-long experience!"
Twain has been cited for his single-blind reliability test in the scientific literature. Here are a few other cites to Twain's scientific results from Google Scholar.
It is the ability to make reliable predictions that is the hallmark of science. I would also note that you don't have to have a PhD to practice the scientific method. Twain was doing science, and his only qualification was his ability to see the con.