Actually, it’s not “quite obvious.” Look closely at the passage cited:

“The habitual use of the active voice, however, makes for forcible writing. This is true not only in the narrative concerned primarily with action but in writing of any kind. Many a tame sentence of description or exposition can be made lively and emphatic by substituting a transitive in the active voice for some such perfunctory expressions as ‘there is’ or ‘could be heard’”

This passage directly says that “the habitual use of the active voice… makes for forcible writing.” It does not say: *certain* uses of the active voice make for forcible writing; instead, it implies that the active voice itself is responsible for forcible writing, presumably in all or most cases (unless we are later told otherwise).

Then, we are told that we can substitute a “transitive in the active voice” in the examples that follow. We are not told that we can substitute a transitive in the active voice for ANOTHER active voice phrase, even though that is actually what’s going on in the examples. Since we were told that the active voice makes forceful writing, we might reasonably conclude that the sentences to be corrected did not employ the active voice.

A reader who already knows grammatical terminology will realize that the third sentence is limiting the first. But someone who doesn’t know grammatical terminology and its applications very well would assume that a paragraph which is endorsing the active voice and encouraging a substitution of a “transitive in the active voice” would probably be correcting examples that are NOT in the active voice. An uneducated reader wouldn’t necessarily realize, given the way this paragraph is written, that there are actually good and bad examples of active voice usage. Nor would they realize that some of the examples following a paragraph endorsing the “active voice” and “substitutions” involving it are actually ALREADY in the active voice.

In sum, the paragraph cited is completely unclear about the status of these examples. The professor is wrong to say that Strunk & White think they are passive, but the comments here are wrong to claim that the passage couldn’t be interpreted that way for an uneducated reader. The professor may have no excuse, but is his reading “demonstrably incorrect”? Only by assuming facts not in evidence. You can’t prove that S&W understood what passive means on the basis of the quoted paragraph, anymore than the professor can prove that they thought their examples were in the passive voice.

And clearly, on the basis of the nonsense I’ve seen identified as “passive voice,” quite a few other people have interpreted the passage the way the professor does.

Oh, really? Even when that opinion is demonstrably incorrect? Arguments advocating blind submission to authority on the basis of credentials are as unpersuasive, to me, as the rest of your post.

“It’s quite obvious that Struck and White are NOT introducing those four examples as illustrations of passive voice.”

Clearly, the point was whether the Elements of Style discussion is helpful, clear, useful, and correct.

The author of the present article provides at least one argument that the effect of Elements of Style is negative: even if the authors understood the difference between an active and a passive sentence, the example from the writing lab shows that their discussion did not clarify the issue.

Geoff Pullum’s grammar with Rodney Huddleston, “The Cambridge Grammar of the English Language,” is one of the most (and arguably the most) impressive and remarkable scholarly achievements in the field of grammar. It is one of the most comprehensive grammatical descriptions of any language, ever.

The professor can be regarded as an expert and his opinion should be taken seriously.