A Quick Story of Rationalism, Empiricism, and Balance
February 20th, 2011
You may know of Galileo’s battles with the Catholic Church over the earth’s movement around the sun. Recently, though, I learned of the Church’s reaction to his discovery (using a telescope) of four moons around Jupiter.
He published his findings in a treatise called The Sidereal Messenger. Here’s how it was received:
In a very different spirit did the Aristotelians receive the Sidereal Messenger of Galileo. The principal professor of philosophy at Padua resisted Galileo’s repeated and urgent entreaties to look at the moon and planets through his telescope; and he even labored to convince the Grand Duke that the satellites of Jupiter could not possibly exist.
[The professor said:] “There are seven windows given to animals in the domicile of the head, through which the air is admitted to the tabernacle of the body, to enlighten, to warm, and to nourish it. What are these parts of the microcosmos? Two nostrils, two eyes, two ears, and a mouth. So in the heavens, as in a macrocosmos, there are two favorable stars, two unpropitious, two luminaries, and Mercury undecided and indifferent. From this and many other similarities in nature, such as the seven metals, etc. which it were tedious to enumerate, we gather that the number of planets is necessarily seven. Moreover, these satellites of Jupiter are invisible to the naked eye, and therefore can exercise no influence on the earth, and therefore would be useless, and therefore do not exist. Besides, the Jews and other ancient nations, as well as modern European, have adopted the division of the week into seven days, and have named them after the seven planets. Now, if we increase the number of the planets, this whole and beautiful system falls to the ground.”
The philosophy professor thought he had a great argument, even one based in empirical fact:
- There are seven holes in the head.
- There are seven days in the week.
- There are seven metals known from the ancient world.
- Seven is clearly a number precious to the Lord.
- Ergo, there must be seven bodies in the heavens (not counting the outer stars fixed in place in the sphere surrounding the earth).
Padua’s philosophy professor was an extreme rationalist. Despite his appeal to a few carefully-selected facts, once he built his argument he refused to check it against reality. In fact, for him, if this fancy “telescope” revealed contrary evidence, then Galileo must be a trickster or a liar.
As for the “Aristotelians” mentioned, the author isn’t using the term the way I have (Aristotle has inspired many writers, and in many ways). No, these Aristotelians are the Scholastics, medieval natural law philosophers committed to demonstrating the truth of Church doctrine through the use of reason. They are quite literally Robert George’s intellectual forbears.
I bring this up because it’s a great example of how dangerous extreme rationalism can be. I think we see a milder (but equally sloppy) version of it in George’s work, when he starts with a known conclusion (i.e., Church doctrine is correct) and attempts to reason his way toward it, disregarding how well the outcome matches reality.
By the way, a few readers have pointed out the dangers of going the opposite way and embracing extreme empiricism instead. That’s worth remembering. Galileo is also known for his research into falling bodies and the nature of acceleration. He worked out basic principles by combining geometric principles with ingenious measurement techniques (which included using his pulse to count time in the absence of a stopwatch, and using a steady stream of water flowing into a vase, using the volume of water to compare intervals). It’s tough to walk the path between rationalism and empiricism. Robert George and the professor from Padua illustrate what happens when you go too far to one side.