On reliability and validity

From The Last Psychiatrist:

“As anyone who has ever dated a girl who was too much into the occult will tell you, astrology is difficult. It has a highly structured set of rules—math, really—so precise and complex that, theoretically, any two astrologers should independently arrive at the same result, which is correct enough times to keep people from breaking out into hysterical laughter all the time. However, astrology is crap, right? Some other factors explain the few successes. Is the fact that so many schizophrenics are born in the spring related to Mars rising in Orion, or to a virus women contract in the winter? Etc. In other words, just because a system is reliable, doesn’t mean it’s valid.”