I have an idea that star signs based on birthdays might have some general utility in predicting some things on the individual level. I’m not saying that horoscope predictions or Zodiac personality descriptions could withstand scientific rigor, just that I can see some plausible correlations to reality. Or, at least astrology could be recognizing some very general patterns that do exist even if “the stars” are not the reason. I’m not someone who believes that “every myth has a basis in fact,” because that is obviously not true, and I’m not trying to rehabilitate the image of astrologers. I’m just saying it makes an interesting thought exercise.
Here’s a proposition: all other things being equal, people born in the same time of year could tend to act in similar ways. Or, people with birthdays around the same time might be more similar to each other than similar to people born at other times of year, if you could factor out all other differences. It seems plausible that people raised in the same culture, for example with the same holidays, same celebrations and same calendar system, could grow up with some similar personality traits. For example, it seems plausible to me that people with a birthday near Christmas would often have a common experience of getting fewer presents in a year than others did. (Assuming they celebrated Christmases and birthdays.) They might get only one set of presents for Christmas and their birthday, so therefore experienced a childhood of envy of other kids, felt short-changed by their childhoods, or early on discovered other measurements of happiness besides material possessions. Gross generalizations here but there may be something to it.
Along the same lines, if children are born into an education system that has summer vacation, then plausibly children who celebrated birthdays in the summer might have a very different experience than children born during the school year. It may be more isolating or marginalizing for a child to have a summer birthday, so he or she grows up with a different relationship to peers than schoolyear-birthday kids do.
In this case, it’s the cultural and social context that sets up the distinctions, not the actual stars. It would depend on the meanings that are already out there about different times of year. Someone whose life is strongly identified with a certain time of year, and if that time of year has a special meaning, would conceivably have a different sense of self than someone who identifies with another time of year. Again, all other things being equal.
This is aside from the force of expectations or power of suggestion that the astrology system itself may set up. It could be that if you are told your entire life that as a person born at X point in time you must have the personality traits Y and Z, that could actually make someone have those characteristics. It could be a case of predictions making themselves true. At the very least there could be a confirmation bias at work. People may notice the things their sign charts say that are accurate much more than what they get wrong.
I could also see a testable biological correlation here somewhere. I think the likelihood is small, but it’s a question that could be tested empirically. All other environmental factors being equal, there could be some developmental similarities in utero among people born at the same time of year. I could imagine this being true especially in pre-industrial agricultural societies where there may be more and better food at some times of year and not others. Different parts of the year might mean different maternal nutrition, different levels of maternal exercise, different forms of stress, all of which could theoretically translate into different birth outcomes and even different early development. Possibly as a winter newborn one’s infant experience could be very different from that of a summer newborn and this could have an impact on personality. Surely giving birth at a time of less sunlight could increase the chance of post-partum depression, which could have a long-term effect on a newborn. (This is only focusing on mom and baby, I realize, but it’s just by way of example.) It’s a bit of a stretch, but you could say that celestial bodies do influence personality, if you include the sun and the tilting of the earth in creating seasons.
There could also be other similarities that are already built into the fact that two people are born at the same time of year. Having the same birthday means, on average, being conceived at the same time of year, so presumably people with the same birthday may already have parents who are similar in their behavior. For example, two people born nine months after Valentine’s Day could both be raised by parents who are conventionally romantic, which could translate into similar parenting.
I recently had a conversation with someone who joked about what his daily horoscope predicted for him that day, and I replied that I hope he had the correct birthday for himself, or else he would be prepared for the wrong thing. I didn’t think about that before I said it, it just came out, and then it hit me: how do you really know what your birthday is? I don’t remember my birth, so I’m dependent on other people to tell me when it was. (I suppose even if I claim to remember the day, my memory could be faulty.) My birth certificate tells me what day it was, but it’s just a piece of paper and paper can be forged. If a birthday-based astrology system is accurate, it won’t be fooled by an incorrect birthday, because the stars know the truth, right?
It occurs to me that the whole birthday epistemology question is a good basis for testing the accuracy of a birthday-based astrology system. Theoretically, instead of starting with your birthday, an astrologer could start with other information about your life and work backwards to predict accurately what your birthday is. Astrology could verify the accuracy of one’s birth certificate, in principle. It’s possible that if the horoscopes are accurate then a long-term survey of your daily horoscope could reveal that your birthday is in fact not the one that you thought but in another month entirely. (Does anyone who follows the star signs come to imagine that his birth certificate is wrong?) Or, you could simply monitor what happens to someone around you and figure out that person’s birthday if you didn’t know it already.
Of course, if all these non-star factors (seasons, holidays, agricultural rhythms) are true, you would need totally different prediction systems for different religions, cultures, climates, and regions. If your personality or destiny really is linked to visible star formations or the solar seasons, then you would clearly need a separate system for the southern hemisphere. I don’t know what to tell you if you’re born in Australia and you’re not sure what your birthday is, but I might come to some conclusions about you if you celebrate Christmas….