Philosophy of Science 134E
Instructor: Christian Lacroix
Nov. 2, 2004
An example of paradigm shift
The Copernician revolution
In about 150 years, we went from the geocentric view of Ptolemy, backed by the Aristotelian worldview and the Catholic Church, to the heliocentric view of Copernicus, as modified by Galileo and explained by Newton.
Today it seems like the heliocentric view is obviously better than the geocentric one, a triumph of reason over dogma, but Kuhn argues that at the time it was not obvious at all. 

Things in favour of Ptolemy’s view
1- Fits the observation that we do not feel the Earth to be in motion and planets and stars seem to move around it.
2- Offers a reasonably accurate means of predicting the motions of the planets which was successfully used for centuries.
3- To have the Earth at the center of the universe fits well with the idea that it was specifically created for us by God.
4- Allows Heaven to be located literally above the Earth.
5- It is compatible with Aristotle’s account of the natural motions of the heavenly bodies, which give a neat explanation of what we can observe in the sky.

Reasons 1 and 2 are based on empirical experience, and reasons 3-5 are based on the compatibility of Ptolemy’s view with other strongly held views.

Normal science
For centuries people used Ptolemy’s view, along with Aristotelian physics, to explain and predict the motion of planets and stars.  This was a time of normal science.
This paradigm faced some anomalies because the orbits of the planets did not seem to be perfect circles, as the theory predicted.
However, it was possible to accommodate this fact by using epicycles to modify the main circle so that the resulting orbits fit with observations. 
This provides an ongoing research program for astronomers.  As an astronomer working under Ptolemy paradigm, your job is to make ever more precise observation of the paths of planets, and to add epicycles where needed to make the theory fit with the observations.

Crisis
The anomalies build up.  The complexity and the number of competing versions of the Ptolemaic theory increase.
This, along with increasing social pressure for calendar reform, leads to the perception that the paradigm was in crisis.
But this is not enough to lead to a revolution, for there are no suitable alternative.

A new paradigm: the Copernician view
An heliocentric alternative to the geocentric Ptolemy’s view.
It was supported by people like Kepler, Galileo, Descartes, and others.

Things in favour of the Copernician model
1- Mathematically simpler
2- After Kepler published his laws of motion (but only after), the heliocentric view became a significantly more empirically adequate theory.

Problems with the Copernician view
1- Initially, Copernicus’ theory was no more accurate than Ptolemy’s.
2- Some predictions of the model are not observed:
	- Venus should sometimes appear six times as large as other times.  This was not 	observable with the naked eye.
	- The model predicts a stellar parallax effect, which was not observed by using the 	most accurate instruments available at the time.
3- There are (apparently) good arguments against it:
	- The “tower argument”
	- Why are not objects on the surface of the Earth thrown off the Earth, like objects 	on the rim of a wheel are when you spin it?
	- Why does not the Earth leave the Moon behind, if it moves?
4- Does not fit well with theology.
	E.g., location of Heavens; somewhat at odds with the idea that Earth was created 	specifically for us.
5- Contradict the best physics of the time, i.e., Aristotle’s.

Paradigm shifts are not purely rational
Kuhn argues that those who accepted the Copernician view had no good reason for it.
Rather, they were influenced by their personality and other considerations
	E.g., whether you favour mathematical simplicity or prefer coherence with the 	overall world-view and conformity to common sense. 

Personal influences in paradigm shifts
- Copernicus prized mathematical simplicity, and had the mathematical ability to formulate the heliocentric alternative precisely.
- Galileo was enough of a rebel to take on the Church, even when the consequences for his life were unpleasant. (Though he eventually backed off.)
- Kepler had a mystical belief in the basic mathematical harmony of the natural world which made him prefer simple elliptical orbits to complex circular ones, and he had access to more detailed astronomical data than anyone before him (he got them from Tycho Brahe).
- Descartes had developed a physics that was radically different than Aristotle’s, and had an explicit philosophical agenda that went much beyond the available data.

Kuhn and the demarcation problem
Is there a difference between science and pseudo-science for Kuhn?

“They had […] achieved a paradigm that proved able to guide the whole group’s research.  Except with the advantage of hindsight, it is hard to find another criterion that so clearly proclaims a field a science.”
Kuhn (1962), p.22 (p.69 in the course pack)

The case of parapsychology
Parapsychology is a science
	Robert H. Thouless, psychologist

Parapsychology is not a science
	Daisie Radner and Michael Radner, philosophers

Parapsychology is a science
Parapsychology is a pre-paradigmatic science.
Parapsychology is a new field, so no central theory yet.  No theory means no paradigm.
But there are many observations that count as “anomalies”.
Other scientists’ resistance toward the acceptance of ESP is like the resistance of scientists toward anomalies.
Other scientists will be convinced not by more proof that ESP exists (i.e., by more anomalies), but by a theory explaining these phenomena.
Still, ESP scientists should not aim at creating a paradigm yet; a paradigm will naturally emerge from more precise research.

Parapsychology is not a science
Parapsychology is not normal science, since it does not have a paradigm.
Parapsychology is not even pre-paradigmatic science because ESP scientists are not looking for a theory.
	Compare with early paleontology.
The few laws parapsychology has are only use to classify phenomena as ESP, never to exclude phenomena as ESP.
They only exclude data when confronted with an obvious fraud.

Kuhn and the demarcation problem
Can the notion of paradigm be used to solve the demarcation problem?
Compare with astrology.