Galileo Channels Plato
Galileo's Dialogue, Day 2, Part 4
As I wrote in a recent post, I intend to write posts for each of the four days in the Dialogue Comparing the Ptolemaic and Copernican Systems1, the book that got Galileo in trouble with Rome. This is the fourth post about Day Two, the longest day in the Dialogue. Here are the previous posts:
Day One: Galileo Dismantles Aristotle's Separation of Earth from the Heavens.
Day Two, Part 1: Galileo Attacks Aristotle’s Followers.
Day Two, Part 2: Galileo Insists the Earth is Spinning on its Axis.
Day Two, Part 3: Galileo on the Acceleration of Falling Bodies.
I have written a fair bit about Galileo’s rôle in the dismantling of the Aristotelian universe and in criticizing the contemporary Peripatetic philosophers. So it is natural to ask what was Galileo’s attitude towards Aristotle’s predecessor and rival, Plato. The answer comes out clearly in the Dialogue. First, Galileo is supportive of Plato and Archimedes, the greatest Platonist scientist of Antiquity, in insisting on the importance of mathematics in physics. Second, the topic of this post, Galileo refers on more than one occasion to Plato’s theory of recollection, outlined in the Phaedo and other dialogues.
For example, during the exchange about what will happen should a stone be dropped from the top of a mast on a moving ship, Simplicio and Salviati have the following exchange.
Simp: So you have not made a hundred tests, or even one? And yet you so freely declare it to be certain? I shall retain my incredulity, and my own confidence that the experiment has been made by the most important authors who make use of it, and that it shows what they say it does.
Salv: Without experiment, I am sure that the effect will happen as I tell you, because it must happen that way; and I might add that you yourself also know that it cannot happen otherwise, no matter how you may pretend not to know it — or give that impression. But I am so handy at picking people's brains that I shall make you confess this in spite of yourself. [p.145]
Note how Salviati tells Simplicio, “I might add that you yourself also know that it cannot happen otherwise.” This theme of recollection recurs when Salviati and Simplicio are discussing what will happen to a stone once it leaves a sling whirled around a thrower’s head:
Salv: The unraveling depends upon some data well known and believed by you just as much as me, but because they do not strike you, you do not see the solution. Without teaching them to you then, since you already know them, I shall cause you to resolve the objection by merely recalling them.
Simp: I have frequently studied your manner of arguing, which gives me the impression that you lean toward Plato's opinion that nostrum scire sit quoddam reminisci (our knowing is a kind of reminiscence). So please remove all question for me by telling your idea of this.
Salv: How I feel about Plato's opinion I can indicate to you by means of words and also by deeds. In my previous arguments I have more than once explained myself with deeds. I shall pursue the same method in the matter at hand, which may then serve as an example, making it easier for you comprehend my ideas about the acquisition of knowledge.... [pp.190-191]
After a back and forth discussion, there is this amusing exchange:
Simp: Let me think a moment here for I have not formed a picture of it in my mind.
Salv: Listen to that, Sagredo; here is the quoddam reminisci (kind of reminiscence) in action, sure enough. [p.191]
Salviati is reminding both Simplicio and Sagredo that this kind of reminiscence comes up completely naturally. Galileo is continually channeling Plato.
I shall return to the topic of Galileo and Plato in a future post when I examine the writings of Alexandre Koyré, the twentieth-century historian of science.
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Galileo Galilei. Dialogue concerning the two chief world systems — Ptolemaic and Copernican. Translated by Stillman Drake, foreword by Albert Einstein. University of California Press, 2nd ed., 1967.