Scientific Revolutions #5

In The Essential Tension Thomas Kuhn posits five characteristics of a good scientific theory to guide theory choice.

1. It should be accurate within its domain, that is, consequences deducible from a theory should be in demonstrated agreement with the results of existing experiments and observations.
2. It should be consistent, not only internally or with itself, but also with other currently accepted theories applicable to related aspects of nature.
3. It should have broad scope. Its consequences should extend far beyond the particular observations, laws, or sub-theories it was initially designed to explain.
4. It should be simple, bringing order to phenomena that in its absence would be individually isolated and, as a set, confused.
5. It should be fruitful of new research findings. That is, it should disclose new phenomena or relationships among those already known.

Kuhn adds: "Nevertheless, two sorts of difficulties are regularly encountered by the men who must use these criteria in choosing, say, between Ptolemy's astronomical theory and Copernicus's, between the oxygen and phlogiston theories of combustion, or between Newtonian mechanics and the quantum theory. Individually the criteria are imprecise: individuals may legitimately differ about their application to concrete cases. In addition, when deployed together, they repeatedly prove to conflict with one another; accuracy may, for example, dictate the choice of one theory or the choice of its competitor" (324).

In The Rationality of Science W. H. Newton-Smith presents his good-making features of theories as follows.

1. Observational nesting. A theory ought to preserve the observational successes of its predecessors. This is the primary indicator of increasing verisimilitude.
2. Fertility. A theory ought to provide scope for future development.
3. Track record. This fertility looking back. The longer the theory exists, the most important its track record.
4. Inter-theory support. That is, it supports other good theory and doesn't clashing with it.
5. Smoothness. Successful fine-tuning or corrections can be achieved in the face of failure.
6. Internal consistency.
7. Compatibility with well-grounded metaphysical beliefs.

He says many scientists and philosophers include simplicity as a good feature, but he discounts it because relative simplicity to a large extent lies in in the eyes of the theoretician and not in the theory. Quantum mechanics surely does not meet this criteria (226-31).