The bad news is that pseudoscience can't be eradicated. "It's not a pathogen or a germ that we can cure from American culture," he said. "It's more like a cancer." If scientists try to emphasize some distinguishing trait of science, pseudoscientists will try to copy it. If being published in a peer reviewed journal is important for science, then pseudoscientists will create their own peer reviewed journals devoted to ESP, creationism, or cold fusion. If testability is the key, the pseudoscientists will claim to have passed one.

Gordin's book is called The Pseudoscience Wars: Immanuel Velikovsky and the Birth of the Modern Fringe, and as the title implies, he centers his case on one particularly charismatic 20th century peddler in pseudoscience.

Though Velikovsky is largely forgotten today, he was the author of a 1950 super-bestselling book,Worlds in Collision, which put forward the idea that in 1500 B.C., Jupiter spat out a comet, which upset the Earth's axis and later became the planet Venus. The book attempted to make the case that this solar system reshuffling caused various mythological catastrophes, such as the parting of the red sea in the Bible.

Gordin used Velikovsky's astronomical tall tale to assess the way scientists distinguish themselves from fringe elements and other outsiders. Many scientists, he said, embrace the concept known as falsifiability. The idea comes from a philosopher of science named Karl Popper, who defined scientific ideas as ones that could be tested and potentially proven wrong.

Einstein, for example, passed Popper's test with flying colors. He made several specific predictions regarding relativity – one of the most famous being the bending of starlight by the sun, which was observed during an eclipse.

Gordin isn't sold on falsifiability as a universal test of science, though he concedes it is powerful and smart. "It captures our intuition," he said. When people weasel out of arguments by changing or adding on to their theories ad hoc, he said, it feels like cheating. Most of us feel frustrated and cheated when we're trying to argue with people who react to every counterexample by reshaping their ideas or inventing special exceptions as they go along.

Popper, said Gordin, felt just such frustration with Freudian psychotherapy. Proponents came up with an exception or new rule to encompass anything that seemed to disprove that it worked. "This enraged Popper," said Gordin. By showing there was no test that could ever disprove it, Popper demonstrated that psychotherapy wasn't rigorous enough to count as science.

This is not to say that psychotherapy is useless, said Gordon. Before Freud, people were categorized as either sane or insane, and Freud introduced the modern idea of mental health as a continuum. Freudian psychology is full of weird, unscientific ideas, but parts of it represented an advance over what people previously believed.

And alas, said Gordin, Popper's falsifiability idea is losing its potency. Since the need to pass tests or make predictions is the current gold standard of science, pseudoscientists are now devising tests and predictions. Earlier this year, for example, the proponents of a brand of creationism known as "intelligent design" claimed a victory after the results of a new analysis of human DNA called the ENCODE project.