Can someone please help me understand the sentence "The book sold 500 copies." Is this sentence correct as is? I am having trouble understanding what the book sold 500 copies of. Of itself?

It is a bit idiomatic. The meaning is that 500 copies of the book were sold.

The bread is baking now.
The trees blew in the wind.
The door opened silently

There is probably a name for this structure; if so, I have forgotten it.
In the expression, the books sold => the verb “sell” is in the intransitive mode => to be sold or be on sale. The following is a definition of “sell” from the American Heritage Dictionary.

Sell sold (sold) selling, sells verb, transitive

1. To exchange or deliver for money or its equivalent.

2. To offer for sale, as for one's business or livelihood: The partners sell textiles.

3. To give up or surrender in exchange for a price or reward: sell one's soul to the devil.

4. To be responsible for the sale of; promote successfully: Publicity sold that product.

5. To persuade (another) to recognize the worth or desirability of: They sold me on the idea.

verb, intransitive

1. To exchange ownership for money or its equivalent; engage in selling.

2. To be sold or be on sale: Grapes are selling high this season.

3. To attract prospective buyers; be popular on the market: an item that sells well.

4. To be approved of; gain acceptance.

Excerpted from The American Heritage® Dictionary of the English Language, Third Edition © 1996 by Houghton Mifflin Company.
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<...a name for this structure...>

I think "sell" in this usage is an "ergative" verb. An ergative verb is an intransitive usage, where an active form has a passive sense. Thus the subject of the verb is not the agent in the action:

1. The book sold very well.

Here, "The book" is the subject of "sold", but it does not perform the action. The agent in the action (the bookseller) is not mentioned.

Beth Levin (English Verb Class and Alternations) calls this the middle construction.

She mentions another construction -- alternation between causative and inchoative -- with the notation that another name for this one is "ergative". She lists "sell" as impossible in the ergative construction. The requirement for an adverb seems to be crucial in disambiguating the two classes in some cases. Thus, in her opinion at least,

I broke the cup.
The cup broke. (break can be ergative.) (meaning: the cup became broken)

I sold the book.
*The book sold. (sell can't be ergative.) (meaning: the book became sold)

The book sold (very) well. (sell can be used in the middle construction)

There is a great deal of confusion in this area, with different authors defining these terms differently: middle voice, ergative, unaccusative. I avoid them all whenever possible!


That's a useful test. (Though I can imagine saying "Did it sell?".)

"Middle voice" troubles me because it's used in Greek for a reflexive form, as in "I wash myself"; also for "I do X for my own benefit" (now why don't we have that one).

I remember reading somewhere that the test for an unaccusative was whether it could be passivised – e.g. "die", "fall".

Anyway, that gives us at least three of these active subject-isn't-the-agent forms:

1. The cup broke – ergative.

2. The book sold well – middle (needs adverb).

3. He died last night – unaccusative (can't be passivised).

Are there any more in Beth Levin, Jim?

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Any more?

I honestly don't know. The book isn't organized that way. My comments were based on a few of her interspersed remarks, references, and footnotes throughout the book. The book is basically a list of verbs classified into groups on the basis of which transformations they can take, for example "Verbs of Combining and Attaching", "Verbs of Preparing", "Verbs of Appearance and Disappearance", "Verbs of Assessment", "Verbs of Communication".

The book is poorly indexed, unless you want to look up a specific verb, but I did find this remark in the section on Passive Alternations:

"It has also been proposed by Perlmutter and Postal (1984) that only unergative verbs (those intransitive verbs whose surface subject is an underlying subject) and not unaccusative verbs (those intransitive verbs whose surface subject is an underlying object) are found in prepositional passives. But not all supposedly unergative verbs allow prepositional passives; these restrictions must be explained."

Some examples precede this discussion:

George Washington slept in this bed. (unergative verb)
This bed was slept in by George Washington.

A pirate ship appeared on the horizon. (unaccusative verb)
*The horizon was appeared on by a pirate ship.

According to these definitions I take it that the deep structure of the unaccusative structure above is thought to be:

(null subject) appeared a pirate ship (=object)

And if die is unaccusative, the deep structure of Mr. Smith died is something like

(null subject) die (+ past tense marker) Mr. Smith (=object)

It's too much for my brain just now, and I haven't got the time nor the inclination to pursue it in any greater detail at this time!


P.S. Levin doesn't use the term "middle voice", though I may have slipped and used it above. She carefully avoids that, preferring the term "middle construction".
That's a useful test.

Yes, especially the adverb easily, and apparently the aspect is equally important, these middle constructions favoring the habitual or timeless simple present.

The meat cuts easily.
This fabric soils easily.
Idaho potatoes bake beautifully.
Copper rods bend easily.
Labels tape easily to that kind of cover.
That door opens easily.