enter image description hereSo I was trying to refresh my memory about grammar using English Grammar for Dummies and I came across this sentence.

A strong light is necessary to sew well

According to the author, this sentence is grammatically incorrect because it lacks a subject even though it sounds right.

Isn't "A strong light" the subject, "is" the linking verb and "necessary" the predicative What is the difference between for example

a strong light is necessary


I am Chinese

Thank you for your time

edit: I added a picture of the relevant page to provide more context.

  • 2
    It seems fine to me.
    – Hot Licks
    Commented Apr 4, 2020 at 2:57
  • 5
    Or else the author was incompetent, as is frequently the case with English textbooks written by English teachers who have learned and teach by rote. Commented Apr 4, 2020 at 3:52
  • 3
    Did you cite the title of the book correctly? Are you sure the title is not English Grammar by Dummies?
    – JK2
    Commented Apr 4, 2020 at 4:52
  • 1
    @Mari-LouA If example B in the book is not correct, is this also incorrect? a permanent nationwide cease-fire is essential to tackle COVID-19 (From New York Times).
    – JK2
    Commented Apr 4, 2020 at 6:24
  • 1
    @Mari-LouA Then, the book itself is just plain wrong. I think this question should be closed because it is based on the erroneous book.
    – JK2
    Commented Apr 4, 2020 at 7:39

4 Answers 4


I think this is a typical case of hypercorrection.

The author claims that

(1) To sew well, a strong light is necessary.

is incorrect because you don't know who's sewing. The correction suggested is inserting the agent you. So, let's just do that to see if that's the problem.

(2) For you to sew well, a strong light is necessary.

I'm sure the author would say (2) is now correct. But I'd say For you here is not required and is even bordering on redundant, if you're referring to any person in general by you.

Then, why did the author think you is necessary when it isn't? Because the author doesn't know this:

Most non-finite clauses have no overt subject, but the interpretation of the clause requires that an understood subject be retrieved from the linguistic or non-linguistic context.

-The Cambridge Grammar of the English Language (Page 65).

(Boldface mine.)

Since the understood subject you is not retrievable from the linguistic context in (1), the question is whether it is retrievable from the non-linguistic context, by which I'm sure CGEL means knowledge that resides outside the discourse.

And the answer is yes, unless the non-linguistic context dictates that the understood subject is anything but 'any person in general' (e.g., a particular person), in which case the author should have mentioned such non-linguistic context before labeling (1) and its variant as "incorrect", but they didn't.


Basically, the author is either an idiot or has his shorts too tight.

While in a total vacuum the sentence would be a bit weird, it would be perfectly idiomatic in the context of, say, a description of how to sew.

In writing, context matters!

  • 1
    To discuss sewing fittingly, joined-up writing is required. Commented Apr 4, 2020 at 14:39
  • 2
    @EdwinAshworth - You're saying it should be seamless??
    – Hot Licks
    Commented Apr 4, 2020 at 15:06
  • 2
    You certainly shouldn't lose the thread. Commented Apr 4, 2020 at 17:00
  • 1
    Stop needling one another.
    – WS2
    Commented Apr 5, 2020 at 6:47
  • 1
    @HotLicks Me? Well I'll be darned!
    – WS2
    Commented Apr 5, 2020 at 20:28

It's not grammatically wrong, it has a grammatical subject:

A strong light is necessary to sew well

The implicated subject is the vocative you:

A strong light is necessary [for you] to sew well

The only example where the grammatical subject is omitted {or grammatically permitted} is in the imperative you form:

(You) Go to Sleep!

However, sometimes people colloquially leave out the grammatical subject and use the implied subject if the context wills it:

[vocative You] Got something to say?
[I] Am too!
[I] Am not!

I think what the author means it that the implied subject is not clear, but it is evident there is a grammatical subject. Therefore, grammatically OK. The syntax structure of the OP's sentence typically occurs in English proverbs or proverbial sayings:

A picture is worth a thousand words
Beauty is in the eye of the beholder


Just an opinion, not a definite answer.

What I think the author trying to express was;

‘A strong light’ is not the only thing needed to sew well (for the given context it was incomplete, ungramatical).

You need further complement (as in what is or who is) to stand a fact that a ‘person’ which actually does need a light to sew well as for machine, it doesn’t.

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