Philosophy of Science 134E
Instructor: Christian Lacroix
Nov. 25, 2004
Why Astrology is a Pseudoscience
Paul R. Thagard
–	Philosophy, psychology, and computer science professor at Waterloo.
–	This paper was published in 1978.
–	Use astrology as an example to illustrate the difference between science and pseudoscience.

Why look at astrology
Most philosophers and historians of science agree that astrology is not a science.
However, there is no consensus as to why.
Neither verificationists (i.e., sophisticated inductivists/logical positivists) nor falsificationists can offer good reasons to say that astrology is a pseudoscience.

What is astrology
More than just what is in the newspapers and magazines.
A full horoscope deals not only with sun signs, but also with the “influences” of the moon and planets, as well as considering the ascendant sign and other matters.
To determine one’s full horoscope, one needs accurate knowledge of the time and place of birth.

A little history of astrology
Originate in Chaldea, thousands of years B.C.
By 700 B.C., the Zodiac was established and a few centuries later the signs were very similar to those of today.
Astrology got to Greece and Rome, and became very popular during the fall of the Roman Republic.
It became increasingly codified, culminating in Ptolemy’s Tetrabiblos (2nd century A.D.) which describes in great details the various influence of the sun, moon and planets.  It is still a fundamental textbook of astrology.
It still flourished during the European Renaissance, along with alchemy and the rise of modern science (e.g., Kepler worked as an astrologer as much as an astronomer), and stayed popular through the 17th century.
Astrology lost its popularity during the Enlightenment (18th century).
Since the 1930’s, however, astrology has regained popularity (e.g., most people know their sun signs).

1- Why astrology is a pseudoscience
Bok, Jerome, and Kurtz (1975)
–	Their statement was signed by 192 leading scientists, including 19 Nobel Prize winners.
Three main reasons:
1- Astrology originated as part of a magical worldview.
2- The planets are too distant for any real physical influence on people.
3- People believe in it only out of longing for comfort.

Thagard’s reply to 1.1
Astrology originated as part of a magical worldview.
Reply: Origins are irrelevant to the scientific status of a theory.
E.g., alchemy to chemistry, occult beginnings of medicine.
Many great scientists have had mystical influence, including Newton and Einstein.

Thagard’s reply to 1.2
The planets are too distant for any real physical influence on people.
Reply: the lack of known physical foundation does not make a theory unscientific.
E.g., when Wegener proposed continental drift, no mechanism was known.
E.g., even though a connection has been established statistically, the physical link between smoking and cancer is unknown*.

Thagard’s reply to 1.3
People believe in it only out of longing for comfort.
Reply: Why someone believe in something is irrelevant to the status of the belief.
Many people believe in good theories for bad reasons.
Even if many people believe in astrology for bad reasons, there might be good reasons available.

2- Why astrology is a pseudoscience
Sophisticated inductivists/logical positivists
Verifiability: a theory is scientific only if we can specified conditions under which it can be verified or tested.
Astrology is not verifiable.

Thagard’s reply to 2
Astrology is not verifiable.
Reply:
The criterion of verifiability does not work.
•	No precise yet successful definition exists.
Astrology is vaguely testable.
•	While astrology cannot make precise prediction (tendencies only), some attempts have been made to test it via large scale surveys (e.g., Gauquelin).

3- Why astrology is a pseudoscience
Falsificationism
A theory is scientific only if it if we can specified conditions under which it could be falsified, i.e., turn out to be false.
Astrology is not falsifiable because its predictions are too vague.

Thagard’s reply to 3
Astrology is not falsifiable because its predictions are too vague.
Reply: falsificationism does not work.
The Duhem problem
Falsification occurs only when an alternative theory is available.
Thus, astrology is no less falsifiable than other theories.

Thagard’s view
A demarcation criterion requires us to consider three elements:
1- Theory itself
2- Community
3- Historical context

Theory
–	Astrology itself.
–	The realm of traditional considerations, such as whether the theory is able to predict, explain, and cover the facts.
–	This shows that astrology has some problems.
•	E.g., negative result of Gauquelin for careers, precession of the equinoxes, what to do with planets discovered after Ptolemy (Neptune, Uranus, Pluto), twins, mass disasters.
–	A theory is more progressive when it is successful in explaining more facts and solving more problems.
•	Similar to Lakatos’ criterion
–	Astrology is not progressive.

Community
–	Those who support the theory, in this case, the practitioner of astrology.
–	Considerations such as:
•	Are they in agreement on the principles of the theory and how to go about solving problems
•	Do they care about solving the problems?
•	Are they actively involved in attempts at confirming and disconfirming their theory?

Historical context
–	Considerations such as:
–	The record of the theory over time in explaining new facts and dealing with anomalies.
–	The availability of alternative theories.

To sum up, a theory or discipline which aim to be scientific is pseudoscientific if and only if:
•	It has been less progressive than alternative theories over a long period of time and faces many unsolved problems, and
•	The community of practitioners makes little attempt to develop the theory towards solutions of the problems, shows no concern for attempts to evaluate the theory in relation to others, and is selective in considering confirmations and disconfirmations.

Astrology is a pseudoscience
Using this criterion, Thagard thinks that he can successfully classify astrology, witchcraft, and pyramidology as pseudosciences, while keeping contemporary physics, chemistry, and biology as sciences.

Comparing Thagard’s view
Unlike Lakatos’ view, progressiveness is only one element needed for granting scientific status.
–	I.e., not a sufficient condition.

Unlike Kuhn, who claims that astronomy lacks a paradigm, Thagard argues that astrologists act as if they were doing normal science, while there are more compelling alternative paradigms available (e.g., psychology).
–	I.e., astrology should be in crisis, yet it isn’t.
Astrologers do solve problems at the individual prediction level, but Kuhn is right that they do not attempts to solve theoretical problems at a more general level.

Consequence of Thagard’s view
A theory can be scientific at one time but pseudoscientific at another.
–	E.g., astrology was a science in Ptolemy’s and Kepler’s times, when there was little alternative to explain people’s personality and behavior, but a pseudoscience now.

Potential problem with Thagard’s view
If the scientific status of a theory depends in part on whether there are better alternatives available, then it is subject to a kind of cultural relativism
–	i.e., what counts as science for a group depends on whether better alternatives are known to this same group.

If an isolated tribe of astrologers had had no contact with the rest of the world since the 17th century, would astrology be a science to them?

If we take the notion of availability in a looser sense, should we consider that any existing alternative counts, even if unknown to us, such as one developed by extraterrestrials or by us in the future?
–	All or most of our science could well turn out to be pseudoscience.

Thagard’s reply
The first option is too narrow, the second too wide.
An alternative counts only if it is generally available in the (present day) world.
–	It presumes some kind of communication network to which a community has or should have access.
–	It means that the community has the responsibility to find out about alternative.