The Trial of Galileo
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Galileo Team #3
Discuss how Galileo resolves the problem of interpreting observations when there are alternative explanations (for plantary systems [Team #1] or relative motion [Team #2]) that each concur with the evidence.

  • Discuss the role of simplicity, especially regarding retrograde motion of the planets and the multiple motions of the sun (sunspots).
  • Discuss how to decide between alternative explanations, if both describe the observations. (How does one know when to trust one's senses and when to reason -- for example, if we do not sense a rotating Earth?) In particular, discuss methods for reconciling "appearances" versus "understanding."

Note: On retrograde and sunspot motion, consult Team #1. Ideally, become familiar with the arguments of Team #2 on the concept of relative motion. Focus instead on the principles for deciding between alternative interpretations of our observations.

For additional depth, consider:
> how Galileo differs philosophically with Aristotle (Day 1) and why this is important in 1632.


  • Heilbron's introduction, pp. xvii-xviii
  • Finnochiaro's "Methodological Reflection" in Galileo on the World Systems, pp.335-356.
  • Santillana's "Philosophical Intermezzo" in The Crime of Galileo. pp.55-77.

  • On simplicity, see the Dialogue, pp. 132-144, 396-400, 401-416, 53; Finnochiaro, pp.28-31, Thomas Kuhn's The Copernican Revolution.
  • On deciding between alternative explanations, review esp. pp. 123-144, 295-298, 492-494, conclusion on p. 536.
  • On appearances vs. understanding, review esp. Day 1, pp. 116-121.