Science is an iterative process and so theories that were once widely accepted may later become superseded, but what does that entail? A superseded theory may be thoroughly undermined by its consistent failure to match expectations. Contrary to falsificationism, it usually takes more than a few anomalies to bring down a theory. Theories are part of larger paradigms which have many variations.
Superseded theories are not only no longer accepted but they are virtually lost, except in general references or obscure historical works. Also, those promoting victorious theories may make exaggerated claims about what has been superseded. There may be confusion about what has been superseded and what has not. The purpose of this essay is to clarify these things in a few cases.
While the story of science may be said to begin with the pre-Socratics, modern empirical science started with Bacon and Galileo. The first superseded theory then was Ptolemaic astronomy as the advantages of Copernicanism were realized. Copernicanism was subsequently superseded, too, though this is often not acknowledged. What did these two theories propose?
Ptolemy wrote a treatise in the 2nd century AD called the Almagest, which described an astronomy in which the earth was the center of circular movements of the moon, the planets and the stars. In order to maintain this paradigm but conform more closely with observation, epicycles (circles on top of circles) were added to these circular orbits. In ancient and medieval times circles were considered the most perfect geometric form. Because the celestial bodies were idealized, there was a strong desire to understand them in terms of circles. The use of epicycles enabled people to maintain this idealization and conform to observation.
The geocentric paradigm of Ptolemy and those who followed him was challenged by the heliocentric astronomy of Copernicus (1473-1543). Galileo (1564-1642), Kepler (1571-1630), and Newton (1643-1727) proposed theories that were further developments of the heliocentric paradigm.
Copernicus wrote that the sun was the center of circular movement of the planets and the stars. Galileo showed how the heliocentric paradigm could reduce the number of epicycles needed. Kepler showed that the planetary orbits were elliptical. Newton placed the planetary orbits into a comprehensive theory of motion by an inverse square law of gravitation.
So Copernicus was vindicated in the sense that the heliocentric paradigm proved more fruitful than the geocentric paradigm. However, his assertions that the orbits were circular and that the sun was the center of the motion of the stars have been superseded.
Has the geocentric paradigm been completely superseded? In so far as it requires the earth to be the center of movement of celestial bodies other than the moon, yes. But there are other senses of the term “center”, notably a center of mass. The validity of a universe with a center of mass is disputed but has not been superseded and so should be considered an open question.
Aristotle’s biological writings were quite empirical for his time. He classified organisms into genus and species and speculated on the purpose (teleology) of the diversity of life. Hippocrates and Galen wrote about medicine. Jumping ahead to the 18th century, Linnaeus developed a biological taxonomy in 1735, and variations of this have been in use ever since. Like those before him, Linnaeus conceived of species as fixed life forms within a hierarchy.
This paradigm of life forms emphasized completeness and stasis: all possible forms of life were included and change over time was excluded. So it was a problem when fossils were found that seemed to be from organisms that no longer existed, because that would imply there were gaps which was considered to be a waste or loss that God would not allow. Or it meant that species had changed.
In the 19th century, the main current of science abandoned both completeness and stasis: many but not all possible life forms have existed and these have changed over time via what Darwin’s followers called evolution. The pendulum of science had swung in the other direction.
Darwin’s criticisms were leveled at a simple version of his opponents’ paradigm in which no species ever changed. But this paradigm was revised to allow some change over time within limits. Darwin and his followers ignored these revisions. The old theory was superseded but the old paradigm was not.
Darwinism prevailed and marched on without opposition until the later half of the 20th century when some scientists started promoting “creation science.” They began working with a paradigm that has never been fully explored: species that have changed within limits of their kind. Initially ignored or vilified by establishment science, they have grown into a worldwide movement.