Criticism of Astrology

Astrology has been widely criticised by skeptics who consider it pseudoscience. This page summarizes some of the most common criticisms.

The Theory

Scientists believe that the underlying theory of astrology lacks any evidential support, and in fact is impossible.

Firstly, there is no known force that can cause celestial objects to affect human life in the way claimed by astrologers (the four known forces of nature can all be ruled out). There is no evidence of any other type of force at work, leaving no mechanism for astrology.1

Perhaps there is some mysterious force at work, unknown to science? Even so, such a force could not work in the way astrology describes because astrology is based on a false understanding of the sizes and positions of celestial bodies. According to astrology, the influence of celestial bodies is more or less evenly spread amongst the most obvious visible heavenly objects. If an object appears brighter or moves in an interesting fashion (e.g. stationary, direct or retrograde), it will tend to be given more significance. This would have made sense 6000 years ago but we now know better. We have learnt that objects we perceive as bigger, brighter, nearer or more active are not necessarily so.

Consider this example: If the outer planets have a similar level of influence to the inner planets, this would mean their level of influence is independent of distance. In turn this means that every planet in the galaxy is also influencing us. The effect of those planets would overwhelm any influence of the planets we can see.

The Evidence

Astrologists claim that astrology does work even if scientists say it can't. Their argument is that scientific knowledge is incomplete and scientists simply don't yet understand how or why astrology works. To answer this, scientists point to the evidence.

In a way astrology is scientific, insofar as that it has a reasonably well defined framework that predicts clear, consistent and testable outcomes. For example, astrology predicts that people born at certain times and under certain conditions will share certain personality traits. However, when studies of these traits are undertaken, no such correlation is found. To date, studies continue to show that personality traits are spread randomly across all star signs.3

Another prediction of astrological theory is that an accomplished astrologer should be able to match people with their birth charts. To test this, astrologers are presented with a series of randomized test subjects and birth charts, then asked to match the subject with their chart. To date no studies have demonstrated an ability to do this better than random chance.3,4

Horoscope Readings

Astrological readings tend to be made up of the following:

• Generalized character assessments that would apply to most people, e.g. "You are family-oriented", "You are mindful of your financial situation", etc.
• Double meanings that are almost always correct because they cover all possibilities, e.g. "You like to be decisive but sometimes you find it hard to make decisions."
• Obvious advice that applies universally, e.g. "Work hard and rewards will come."
• Vague references which could be interpreted in many different ways.
• Most importantly, things the subject wants to hear, e.g. "This is a positive time for romance".

Using these simple tricks, astrologers can create a horoscope reading that will always apply to the reader. Most advice applies to most people, and readers will naturally tend to interpret the readings as being personal to them. A graphic example of this phenomena was provided in a 1979 study by French statistician Michel Gauquelin. 150 people were given a horoscope reading and asked, along with their friends, to rate it for accuracy. 94 percent said the horoscope accurately described their character, and 90 percent of their friends agreed. In fact they had all been given the same horoscope—that of notorious mass murderer Dr Petiot.

Ethics

A less common but quite serious criticism of astrology is that it discriminates unfairly. For example, it is claimed that a number of prominent business people routinely use astrology to assist their decision making, including the hiring of employees1. This would naturally upset applicants who do not believe in astrology. Such discrimination is illegal in most western countries so people who use astrological methods would be inclined to keep their methods secret, making detailed study difficult.