Eric Evans graduated in 2014, and is a frequent contributor to The Johnnie Chair. He frequently visits the Annapolis campus.
St. John’s and Naval Academy have had an annual croquet match for the past 30 years. It is one of the events that make spring time so fun here at the College. Spectators dress up in dapper, Great-Gatsby-like-attire (bow-ties, floral dresses, top-hats, pipes, etc) and cheer on their respective teams with a glass of champagne in one hand and slices of cheese in another. Needless to say, its quite an event. Our team begins to practices in the fall.
The Question: How does classical physics tackle causation?
The Text: Christiaan Huygens’s On the motion of Colliding Bodies, Descartes’s Principles of Material Objects, and croquet at St. John’s
For a Johnnie, I know abysmally little about croquet, so Joe here in the light blue kindly gives me a refresher. But bouncing one ball off another soon takes Johnnies to Huygens and his treatise on elastic collisions, which Joe has just read in Lab.
One major thing Huygens is doing is disputing a weird claim by Descartes: that a small body can’t make a heavier one move, no matter how fast it’s moving! Also that a heavier body can’t be slowed down by a lighter. When I bring this up, Joe laughs and says, “I wonder how anyone could ever think that!”
If croquet leads us to feel that Descartes’s wrong, it still takes Huygens to show us how. In Huygens, a small body has a small effect (not no effect), a large body a large effect. Which helps pave the way for Newton’s third law: “To any action is always an opposite and equal reaction…” Sounds mystical. But it has to be, in order to rebut one heavy consequence of Descartes’s claim: that some actions are too insignificant to cause anything—Hello, global warming!
But because Newton goes mystical, we may think he’s well-founded in treating the universe as one giant cosmic game of croquet. But Joe and I are skeptical: how does Newton’s discussion of physical collisions lead to these enormous claims about ‘any action’? Is the only kind of action in the entire universe physical collision?
When Aristotle describes the Prime (First) Mover, he’s considering precisely the way an exclusively physical account of the world fails. If we believe only in physical cause, looking for a first mover just leads to an infinite regression. But Aristotle’s First Mover isn’t the first mallet swing of a cosmic game of croquet. His First Mover causes motion because it is the good aimed at by all beings in the world. It’s a different kind of cause entirely. The Prime Mover moves like an unmoved thought moves the thinker. Or like a person you’re in love with who doesn’t even know you exist moves you.
The adventure continues… @its.philosophy.time on Instagram
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