Your birthday is an inescapable mark, one of a small number of qualities in life you can never change, that accompanies you everywhere. Think about how often you write out or speak aloud those eight digits; they are one of the core confirmations of your identity, now and forever. I’m “Elijah Wolfson,” but to many I’m also “09/20/1985.”
The immutability of one’s nativity may be why so many are drawn to astrology—according to a 2009 Harris Poll, a full 26 percent of Americans believe in astrology (less than the number of UFO believers, but more than those that accept reincarnation as truth). Astrology builds on your birthday, giving it a meaning that goes well beyond that arbitrary 24-hour period so many years ago, of which you have no functional memory. It purports to help us understand the world through a system of relationships between astrological phenomena and human experience. Today, it takes its most popular form in the horoscope, found mostly in pop culture magazine and websites, and often focusing on foretelling the reader’s future in the realms of love and money.
But astrology was once a wholly scholarly and scientific endeavor. For example, medical astrology, or “iatromathematics,” stretches as far back as the field of medicine itself. “This is one of the longest standing intellectual traditions on the planet,” says Lauren Kassell, professor at the University of Cambridge’s Department of History and Philosophy of Science. Kassell researches the history of astrological medicine. “For centuries it was common practice for educated physicians to use astrology as one of their tools,” she says. Hippocrates, whose namesake oath is, to this day, still sworn to by all who enter the field, has been attributed to the saying “a physician without knowledge of astrology has no right to call himself a physician.”