With most traits, humans fall on different points along a spectrum. If you ask people whether they prefer to think or feel, or whether they prefer to judge or perceive, the majority will tell you a little of both. Jung himself admitted as much, noting that the binaries were useful ways of thinking about people, but writing that “there is no such thing as a pure extravert or a pure introvert. Such a man would be in the lunatic asylum.”
But the test is built entirely around the basis that people are all one or the other. It arrives at the conclusion by giving people questions such as “You tend to sympathize with other people” and offering them only two blunt answers: “yes” or “no.”
We could accept the fact that the Myers-Briggs is limited in defining people in binary categories, but still theoretically get some value out of it because it accurately indicates which pole of any category we’re closest to.
But that idea is tough to swallow given the fact that the test is notoriously inconsistent. Research has found that as much as 50 percent of people arrive at a different result the second time they take a test, even if it’s just five weeks later."