Hello, I’m Dr. Anadale from Mount St. Mary’s University in Emmitsburg, Maryland.
Our text today is excerpts from Galileo’s work The Assayer, published in 1623.
In this work, Galileo argues for using new mathematical tools to know the physical world,
instead of older philosophical tools.
In the first excerpt, from section 24, Galileo disagrees with a man named Sarsi.
Sarsi, he says, seems to think that philosophy depends on the authority of famous authors,
as though the most important thing about a claim is who made it.
But, Galileo writes, “Mr. Sarsi, this is not how the matter stands.”
Instead, philosophy is written the vast book of nature, which is the universe.
To read this book, says Galileo, we need to master the language of mathematics and geometry.
Without the tools of mathematics, we will be unable to grasp any truths from our observation
of the physical world.
I see two main takeaways from this section.
First: observation, not authority, is the key to truth about nature, and second: mathematics
is the key to finding truth through our observations.
The next excerpt, from section 196, deals with Primary and Secondary Qualities.
Galileo begins by examining the concept of heat, saying “I strongly suspect that the
concept which everyone has formed of it is very far from being the true one.
People have come to believe that it is a genuine accident, affection, or quality, which inheres
as something real in the matter which we feel ourselves being warmed by.”
Galileo thinks this common view is mistaken.
He doubts that heat is a real quality that things possess in themselves.
To make his reasoning clear, he distinguishes between two different types of qualities,
which we will call primary qualities and secondary qualities.
First, primary qualities.
Galileo says that whenever I conceive of or think about any material object, I necessarily also
think of it as (1) bounded, or having a shape, (2) being small or large in relation to other
things, or having a size, (3) being in a particular place and time, (4) being at rest or in motion,
(5) as touching or not touching other things, (6) as being one, few, or many, that is, having number.
These six qualities, shape, size, place, motion, contact, and number, are primary qualities,
and Galileo says he cannot “separate it [the thing] from these states by any act of the imagination.”
Let’s pause here and test this claim.
Can you, using your mind, clearly conceive of a piece of matter that does not have a
shape, or does not have size, or a location?
Be careful: the test is not that it has no particular shape or size, but that it has
no shape or size at all.
Please give that some thought before our next meeting.
If Galileo is right, then the concept of “matter” always includes these six properties.
They are inseparable from any material object whatsoever, and are called “Primary Qualities.”
Now let’s go on with Galileo’s text.
He next describes what we call Secondary Qualities.
He says he does not find himself compelled to think of a piece of matter as having some
color, sound, smell, or taste.
Without our senses to inform us of the colors of things, we would never have discovered
them using thought or imagination alone.
In this regard, color, sound, etc. are different from the primary qualities we just discussed.
This is why, Galileo says, he considers these secondary qualities, color, sound, smell,
taste, as “nothing other than mere names,” which “inhere only in the sentient body,” or observer.
That is, color, sound, etc. exist not in the things we sense, but in our minds only.
Is he right about this?
Without an observer, is a lemon still yellow?
Or should we say the lemon has the power to cause yellow experiences in an observer, if one shows up?
To conclude: Galileo says when we encounter physical objects, we perceive both primary
qualities and secondary qualities, but only the primary qualities are real and exist as
properties of the object.
The secondary qualities exist only in our own minds, but “we want to believe that
they also truly exist.”
But this is a mistake we should avoid.
That’s a brief overview of two paragraphs from Galileo’s The Assayer.
I look forward to discussing them with you soon.
Thanks for watching today; goodbye.