My teacher told me that the phrase be necessary to can be used only on people. For example,

Something is necessary to someone.

Assuming she is correct, then this following sentence, the one I want to ask, will be incorrect.

Actually, healthy fats are necessary to our overall well-being.

Which of us is right?

  • The sentence you want to ask is totally fine. – Zairja Oct 15 '12 at 0:55
  • @Zairja I think so too. But I need something to backup when I go to my teacher. – Shane Hsu Oct 15 '12 at 0:56
  • These are some results from a search of the BYU COCA. Certainly not common, but necessary to doesn't seem awkward to me. For Shane's sentence, for may still be preferable. – Zairja Oct 15 '12 at 1:25
  • Did the teacher say that the phrase be necessary to can necessarily be used only on people? You do not have to back up your stand -- the teacher needs to show a convincing reference in support of her statement. There's no such restriction that I know of. – Kris Oct 15 '12 at 4:48
  • @Kris Yeah, that's not how school works in Taiwan...... I personally feel sad that every student in my class feel perfectly all right my teacher's words. – Shane Hsu Oct 15 '12 at 13:08

Your teacher is most likely incorrect.

Old Counterexamples

Some high-profile examples, though dated and not a model for modern grammar, counter the idea that be necessary to may only refer to people.

The Second Amendment of the U.S. Constitution (source):

A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed.

Thomas Paine in Age of Reason (source):

But it is necessary to the happiness of man, that he be mentally faithful to himself.

John Locke in A Letter concerning Toleration (source):

Those moral rules which are necessary to the preservation of civil society [. . .].

New Counterexamples

I did a search of COCA for necessary to the [N*] to obtain the following examples. This is not an exhaustive list. Recent examples include Bloomsbury, Freud, and the Vulgar Passions (1990):

The monetary reforms necessary to the preservation of reasonable price stability are also necessary to the preservation of civilization.

Intermental Thought in the Novel: The Middlemarch Mind (2005):

The physical brain is necessary to the production of a mind [. . .].

"Radical Islam in America" USA Today (2005):

To the contrary, preventing this is necessary to the defense of religious freedom.

American Heritage (2004):

The abdominal operation is necessary to the health of the patient [. . .].

Meet The Press (Spoken) (2011):

Debate that is absolutely necessary to the future of this country in terms of entitlements [. . .].

Microsoft–hardly a paragon of the English language–has an error in Windows 7:

The Selected Disk Is Necessary to the Operation of Your Computer, and May Not Be Cleaned

Examples of the teacher's claim

A COCA search provides a few hits between 1990 and 2010 (source):

He was thinking, from his care in formulating his words, which was more necessary to him with her than it had been with anyone.

What would be more meaningful than being necessary to him in a practical sense [. . .].

She wanted to become so necessary to him that he wouldn't leave her.

She was both intelligent and necessary to him.

I am not so necessary to him as he is to me.

Even if Gorbachev's history was, and still is, necessary to him, it is clearly out of style with many of his successors [. . .].

Note: this only looks at "necessary to him"; further searches with her, them, person names, etc. may yield more examples.


In the OP's case it does sound better to replace to with for; however, the sentences above sound fine to me. My intuitive guess is that the phrase be necessary to (excluding to-infinitives, e.g. "it is necessary to kill") is less common than be necessary for, but I lack evidence to back up that claim. Nevertheless, the teacher's claim doesn't seem founded on real-world usage.

  • @JohnLawler I've updated my answer but welcome additional critique. I would still like to do a thorough search of the BYU corpora and NGrams but it will have to wait until later in the week unless someone else takes up the charge. (: – Zairja Oct 15 '12 at 2:19
  • 1
    I don't think the 2nd Amendment of the US constitution is a good example of writing to imitate. People constantly argue about what it means. My interpretation is: Because a well-regulated militia is necessary {for/to} the security of a free country, the right of the people to keep and bear military arms, so that they can be immediately prepared to go to war if called upon by their government to do so, shall not be infringed. The NRA, millions of American gun-nuts, and many others would disagree. We all have our personal opinions about such things. I'd use for & assume that to is BrE. – user21497 Oct 15 '12 at 5:09
  • @Zairja Thanks for providing such detailed answer. – Shane Hsu Oct 15 '12 at 13:11

I think there is something wrong with your sentence, in that I myself could not use necessary to in that way. It would have to be necessary for, at least if it were me saying it. I would have to say:

  • Healthy fats are necessary for our overall well-being.

Here are some examples from the OED:

  • It was necessary to have a variety.
  • Is is necessary to declare your imported goods.
  • I prepared all things necessary for my journey.
  • Change and alternation are necessary for the mind as well as for the body.

I can’t quite put my finger on it, but your use of necessary to there strikes me as old-fashioned. I am not saying your teacher is right, mind you; there seems to be something left out.

  • I agree it seems stilted or old-fashioned when it occurs. However, it would seem (based on searches of the various forms) that it's acceptable to have to whether it involves a person or not (e.g. "it is necessary to our national security", "tax hikes are necessary to the economy", etc.). – Zairja Oct 15 '12 at 1:18
  • @tchrist: In your first two examples, to is not the preposition otherwise omnipresent in this thread. To have a variety was necessary shows it to be the infinitive marker. – Edwin Ashworth Oct 21 '12 at 13:58

What I've noticed is a difference in what "necessary" is expressing. Necessary can refer to a need, in the sense of something that is a requirement, but it can also function as more of a modal verb, along the lines of the Latin debeo or the Italian devo, which means something along the lines of ought, or must. In English we tend to use have as in "I have to go".

When necessary is performing the first function, we use for, and when it performs the second, we use to.

Thus: "A passport is necessary for travelling", because it is something you need.

While "it is necessary to bring your passport to the airport before you travel", because necessary is modifying the verb that you really ought to perform.

You could use these different words as a quick litmus test. If you can replace "it is necessary" with "there is a need", then it should be "for". If you can replace "it is necessary" with "I have to", then it is "to". That test is a bit loose, but I think it serves to demonstrate my point.


My point of view: -"It is necessary TO do this as soon as possible". "Necessary to" for an immediate action to be implemented ACCORDING TO YOU. -"It is necessary for our well-being". "Necessary for" as an AGREED RECOMMENDATION. -"Computers are necessary for survival" (Source: Google). You describe something as the usual trend, since people RECOMMEND it to act in this way. -"A photo ID is necessary for travelling on domestic flights" (Source: Google) In this case, it is a RULE, it doesn't depend on me. -"It is necessary FOR him to DO it as soon as possible". I recommend HIM to implement something urgently. If anyone disagrees, feel free to comment, but I think that's the answer!

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