Because I took the trouble to research the phrase, I ended up writing "Thanks for providing such a striking example of the problem." Not that I figured out it would be wrong to say "Thanks for the object lesson," but just that I wanted out of that comments thread and into a separate post about the meaning of "object lesson," which explains to me why I'd always felt uneasy about using it. That is, I'd learned it from hearing others use it, but I wasn't convinced they were using it properly.
Here's an example of the way other people use the term. This is Paul Krugman in a NYT column from January 4th: "The past two months have... been an object lesson in the extent to which 'grass roots' anger is actually being orchestrated from the top." And here's the NYT Editorial Board, from early December: "[T]he painfully slow pace of recovery following the last recession provided an object lesson in the limits of relying on low interest rates."
See how flabby that is?! It's an object lesson in... flabbiness!
Now, check out the Wikipedia article "Object Lesson." Historically, "object lesson" is something crisply specific:
An object lesson is a teaching method that consists of using a physical object or visual aid as a discussion piece for a lesson...
The object lesson approach is promoted in the educational philosophy of Johann Heinrich Pestalozzi, who held that teaching should begin with observation of objects which help students recognize concepts. In his teaching and writing he emphasized the concept of Anschauung, which may be understood as “sense training.”
Pestalozzi taught that children were first to develop sensation, then perception, notion, and finally volition, learning how to act morally based on an individual view of the world. Object lessons were important elements in teaching during the Victorian era of the mid- to late-nineteenth century....
Check out this lithograph from the late 19th century, with the title "Object Lesson":
The guy with the furled umbrella is, presumably, giving the object lesson. I've looked at this picture and attempted to understand what the lesson is. I have no idea. Pigs are mammals?
Maybe it doesn't matter. It's just that this guy is seeing something and taking it as an occasion to teach some lesson. The ladies seem to be tolerating the mansplaining. Or — oh! — if we look at the whole picture — and not just the pigs he's pointing out — the entire image is an object for a lesson in mansplaining!
This is a very restrictive meaning for "object lesson," and it's obviously not what people have been using. If we click over to Wiktionary, we see that restrictive meaning, plus the broader usage: "Anything used as an example or lesson which serves to warn others as to the outcomes that result from a particular action or behavior, as exemplified by the fates of those who followed that course."
Now, here's something that came up in my research. A clip — viral recently — showing a snowball fight filmed in 1987:
From a NYT article (last November) about that clip, here's a description of the bicyclist who enters the fray and gets knocked over:
His legs fly up in the air; his hat lands upside down in the snow. Before he can even get up, the cyclist is pelted again, and someone tries to steal his bike — but the cyclist stands and rips it away, then hops back on, abandoning his hat, retreating, pedaling off the way he came, taking powdery sniper fire as he goes. It is an object lesson in futility, in noble intentions thwarted — one man’s vision destroyed by the sudden madness of a crowd.
No one is purporting to teach a lesson using an object, but the author of those words is nudging us to view what happened as the basis for a lesson. We're told what the lesson is in, and we're supposed to teach ourselves the lesson or simply to see, instantly, what the lesson is.
I think, in the present day usage, "object lesson" works as an assertion that the lesson is obvious. You only need to identify the topic of the lesson. There's no teacher taking time, in the presence of the object, leading you — with your mind enhanced by the tangibility of the object — to a new level of understanding. It's just look and aha!
