We are finally in a position to answer the questions with which we began this lecture. Why are disputes between science and religion so persistent, why are they apparently irresolvable, and why do they serve so easily as occasions for emotional reactions?
The Galileo affair is the classic case of these characteristics. His trial took place in 1633, but it still has not really ended. He himself never was able to find a decisive scientific proof of Copernicanism. But within a few generations after his death, heliocentric astronomy received its full theoretical justification in Newton's laws of gravitation, and its decisive empirical proof in the observation of stellar aberration in 1728 and of stellar parallax in 1838. The scientific issue was definitively settled at that point.
And as long ago as the 1820's the Catholic Church agreed, in effect, that Galileo's scientific views were correct. Yet this dispute continues on up into our own day, 33 which has seen a special effort by Pope John-Paul II in the past few years to put a final end to the Galileo affair. This is not a case of beating a dead horse, because this horse is still alive. Why won't this issue die?
The answer is that there are good grounds to be concerned that there could be another Galileo case in the future over some different set of scientific ideas. Although this may sound like a startling thing to say, it follows rather straightforwardly from our main argument in this lecture.