I would like to ask about the formality of the phrase "Do more harm than good".

Could I use it in formal writing such as an essay?

Since it is an idiom, and my teacher said that the majority of idioms are informal, I wonder if there are any exceptions for phrases like this.

Thanks in advance!


2 Answers 2


I think your teacher was trying to be helpful by giving you a simple rule like "don't use idioms in formal writing". But, think of your own native language. Can you write a formal essay using idioms?

I'm going to assume that you can, but it depends on the context. It's the same in English. Some idioms are so common that they are used routinely in any communication. Others are less common, or limited to a particular dialect, and so not appropriate in a formal essay as the meaning may not be obvious.

"More harm than good" is an example of an idiom so common that no one will take any special notice of its use -- as long as you use it correctly. For example:

Patients with life-threatening illnesses often choose to accept the risk that any therapy to cure their condition may do more harm than good. For example, chemotherapy drugs work on the principle that cancerous cells are more susceptible to certain poisons than normal cells, but nevertheless the inevitable damage to normal tissue may leave the body unable to fight off serious infectious disease.

I use the idiom here, but I also explain what is meant by "more harm than good".

  • Thanks Andrew, your answer is so brilliant, and it is even longer than my question. I would say that there is a gap between my first language, which is Vietnamese, and English, meaning that I sometimes cannot manage to use words and phrases appropriately, even though I may know the exact meaning of such phrases. with your answer I think I would be more confident when using common idioms in my essays down the road. thanks again!
    – Ben68952
    Jun 30, 2019 at 16:02

An idiom is a group of words established by usage as having a meaning not deducible from those of the individual words (e.g. over the moon, see the light). "To do more harm than good" has an obvious meaning deducible from the individual words, thus I would not call it an "idiom". The expression is often found in formal writing, especially of a medical type, including when the balance of benefits and drawbacks of medication or other treatments are being discussed. Article in medical journal: "Does immunonutrition in patients with sepsis do more harm than good?"

Idiom (Cambridge Dictionary)

  • Thanks Mr. Harvey, now I got new knowledge about idiom from you.
    – Ben68952
    Jun 30, 2019 at 15:54
  • It turns out a number of prominent dictionaries including Cambridge and Merriam-Webster do classify this phrase as an idiom. The literal interpretation and idiomatic meaning are very similar so it's not obvious to the native speaker.
    – JimmyJames
    Jan 31, 2020 at 21:48
  • Please clarify the difference between the idiomatic and literal meanings that is 'not obvious to the native speaker'. Jan 31, 2020 at 23:35

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