The Logic of “Rain Causes Puddles”

Doubt it if you will, but Vermonters who drive I-91 will be happy, even eager, to tell you they saw the sign. It was broadcast in flashing safety-yellow from the movable roadside signs usually engaged in warnings such as, “Road narrows ahead/Move right” or “Icy conditions/Slow down”. For weeks last fall we were warned, “Rain causes puddles”. That’s all. Just, in all caps, “RAIN CAUSES PUDDLES”.

At some point it occurred to me that this constitutes an enthymeme of one statement. An enthymeme is a syllogism with one or two unstated truth claims; a syllogism is a three statement argument drawing a conclusion about a term by relating it to two other terms.

An example of a syllogism is:

Bushes grown in Pennsylvania will survive in Connecticut’s climate.
All these bushes were grown in Pennsylvania.
Therefore, these bushes will survive in Connecticut’s climate.

An enthymeme is a syllogism that doesn’t have everything spelled out; something is assumed by the speaker. Let’s say I live in Connecticut and am standing in my local tree nursery. I want to be sure the plants I buy will survive in the Connecticut climate. I know he doesn’t grow the bushes here; they are imported from wholesale nurseries elsewhere. The conversations with the owner might go like this:

“Will these survive winter in Connecticut?”

“Anything grown in Pennsylvania will survive in Connecticut. These are Pennsylvania-grown.” (The conclusion is assumed: Yes, these will grow in Connecticut.)

In ordinary communication it might be any of the statements which is assumed. The owner might say, “All these bushes were grown in Pennsylvania, so they will grow in Connecticut,” which assumes I know the climate of Pennsylvania is similar to Connecticut.

Or, if a sign by the plants makes it obvious they are from a Pennsylvania nursery, the owner might assure me by stating, “Anything grown in Pennsylvania will grow in Connecticut, so these will grow here.”

In each of these cases, two statements were stated, and one was assumed. But because we have such a tremendous amount of knowledge, we often get by with one. That nursery man might assure me of the conclusion, These plants will grow in Connecticut, with one statement only: “These were grown in Pennsylvania.” My mind supplies, “Oh, Pennsylvania has similar climate, so they will be fine in Connecticut.”

This is how we think all the time. You make tens of enthymemes a day, I am sure. “I’m running out of time so I’ll drop this errand.” (Assumed: it takes time to do the extra errand.)  “That meeting is for salesclerks only so I don’t have to go.” (I’m not a salesclerk.) “I’d better review Latin because tomorrow’s Tuesday.” (We have a quiz on Tuesdays.)

So, back to “Rain causes puddles”. It is an enthymeme of one statement, a syllogism with two assumed statements that all drivers should know.

 

Rain causes puddles.
Puddles cause hydroplaning.
Therefore, rain causes hydroplaning.

The purpose of this heady piece of reasoning? We are being reminded to adjust our driving accordingly.

To the good-humored traffic controller who programmed that sign, a subtle wit who respects the intelligence of the drivers of this interstate, I wave my windshield wiper in salute.

About lettersfromheartscontent

Mother of six, homeschool teacher, tutor with Classical Conversations, wife to a forester and educator. I tend a perennial garden with a riot of blossoms, ride my bicycle in and out of the watershed, play ocarina and a boom-chick accompaniment when my kids feel like playing contradance music. I love being home, but I love an open road and adventure, too. Classical Conversations' Writers Circle carries my article on some aspect of classical education once a month.
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