“All truth passes through three stages: First, it is ridiculed. Second, it is violently opposed. Third, it is accepted as being self-evident.”

Arthur Schopenhauer (1788–1860)

HOW INTELLIGENT ARE YOU? This is not an easy question to answer. Intelligence is one of those qualities that we think we can recognize in people, but when we try to define it, it can slip from our grasp. If it’s any consolation, there’s no agreed definition of intelligence among the many specialists in psychology, neurology, education or other professional fields who devote a good deal of their own intelligence to thinking about it. There may be no agreed definition, but there are two ideas that dominate popular conceptions of intelligence. The ...

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