I am doing a PhD in physics / applied math and have just started writing the theory section. A large-ish part (5-10 pages, estimated) will be setting the scene with some theoretical tools that I am using but did not invent. These tools will eventually be used as the basis for analysing data.

I will say the word so you don't have to think it: plagiarism. I have absolutely no desire to plagiarize so am very careful about citing my sources - however while writing I get the feeling that I am simply copying off of others.

Question, in two parts:

  1. Can anyone give a strategy for how to write a theory section and make it ``your own'' while clearly citing relevant material?
  2. Is this feeling actually normal and am I just over-reacting?
  • 13
    If this were the definition of plagiarism, then the author of every textbook or thesis would be guilty. There are a lot of choices to do even when you are only presenting material: choosing what to present and what to omit, adopting the best notation, choosing what to prove and how to do it so that the introduction is self-contained... So your introduction will likely not be simply the copy of a textbook, but it will contain lots of intellectual work coming from your neurons. (That said, you still have to cite your sources and give proper attribution, of course.) Commented Feb 29, 2016 at 14:10
  • 5
    How about not writing such a section? The idea of writing a 200-page treatise to get your PhD is absurd, and we should reduce the absurdity by writing less filler in theses. If you have people on your committee who aren't specialists in your field, and will therefore need some general background, initiate a discussion with them. Offer to recommend a review article or chapter of a book that they could read in order to get up to speed. Your job is not to write a textbook or a review article.
    – user1482
    Commented Mar 1, 2016 at 1:30
  • 4
    Dumb question: What is or might be wrong if most of the section is copied as long as you cite correctly?
    – BCLC
    Commented Mar 1, 2016 at 7:17
  • Btw do you really need to write those 5-10 pages? I mean you're not going to introduce limits to someone reading a undergrad paper on linear algebra. Maybe a little review but I'm not sure that be in the intro. I think that you could put the review in the middle whenever the need arises. Perhaps the length of that portion depends on the topics involved. Why not ask your adviser? Oh also no desire to plagiarise is not the same as desire to not plagiarise :P
    – BCLC
    Commented Mar 1, 2016 at 15:22
  • Aren't we all are not just »dwarfs standing on the shoulders of giants«? And ergo "plagiarising" in one way or another, as if every - not cited - thought really is an original one.. Commented Mar 1, 2016 at 19:30

7 Answers 7


Although I'm not in "physics/applied-math", but, rather, "math", I see the same or similar issue arise. Let's consider the point that, by this year, the "context/background/set-up" has very likely been highly optimized, both for effectiveness and for succinctness. Nothing wasted, nothing superfluous, etc. So it is likely to be hard to "improvise" much on its description without making it worse in some way. This may be the case even down to small notational conventions, wording, etc.

So, be absolutely scrupulous in citing, and try to have it all in your own head so that you can write it yourself (not literally copying), even while citing, ... and remarking something like "we recall some standard facts/ideas/set-up, e.g., from [X]."

  • 1
    @tomasz: If you "write from your head", how on Earth do you know they're actually your own words, and not an unconscious quoting from a memory of something you read?
    – jamesqf
    Commented Mar 1, 2016 at 4:51
  • 1
    Dumb question: What is or might be wrong if most of the section is copied as long as you cite correctly?
    – BCLC
    Commented Mar 1, 2016 at 7:16
  • 1
    @BCLC Not necessarily plagiarism in the strictest sense, but it is generally frowned upon to copy large sections and might actually violate the original author's copyright if it is deemed too extensive to fall under Fair Use. Commented Mar 1, 2016 at 9:12
  • 1
    @jamesqf: I don't usually memorise sentences, but ideas. I suppose I could, in an amazing coincidence, use exactly the same phrasing for some parts, but I don't see how I could avoid this sort of "quoting", short of trying to match what I have written to various sources. And that is just silly. Of course, there are also some basic elements which one can only phrase in so many ways, but that doesn't make it a quotation.
    – tomasz
    Commented Mar 1, 2016 at 11:27
  • 1
    Of course, I am talking about standard material you have probably read/heard about in a bunch of different places, which you understand unconsciously. Using standard phrasing for standard things is not a citation and certainly not plagiarism, as long as you make it clear what it is. This is distinct from more novel ideas, for which you have a definitive and fairly recent source.
    – tomasz
    Commented Mar 1, 2016 at 11:38

Given that you've almost finished a PhD in your field, it's fair to say that you should have a solid grasp of the basic definitions and concepts you're trying to write up at the moment. So I suggest you do the following. Close all your textbooks and papers and write that section on your own, without looking at any other sources while you're writing it. That should ensure that you express the ideas mostly in your own words. Then, go back and check your version against the standard references to make sure you didn't get anything wrong and that you've included any relevant citations. If you see that one of the standard sources has explained one of the concepts much better than you did, consider explicitly quoting that source: e.g., "Symplectic widgets were defined by Widgetmeister [Wid83] as [...]".

At the end of the day, though, you don't need to worry too much about this. As long as you cite sources clearly, I don't think anyone's going to complain that your description of the standard material looks a lot like other peoples' descriptions of the same thing, especially if it's not word-for-word the same. Standard material always looks standard and a lot of readers will skip over it anyway. The real contribution of your thesis is in the later sections.

  • 1
    Yep. You need to have mastered this stuff and teaching it is one way to prove it. Nor will the practice re-expressing the basic hurt: you're likely to do a certain amount of that as you go forward, anyway. Commented Feb 29, 2016 at 23:47

This is actually very simple ethically:

You did research work which - by your description - is experimental. You ran experiments, you're analyzing data, you're making conclusions based on the data.

Your research contribution is your conclusions. (and possibly your raw results and experimental setup as well.)

The theory section is not plagiarized because you're not claiming this is your original (theoretical) work. You're summing up what other people have done and discussed.

That's it. Other answers have good suggestions regarding how to approach writing this section.

PS - Sometimes, the cogent presentation of the theoretical background can itself be considered a contribution. But this happens more in textbooks or in review papers, less in theses.

  • This one gets my vote. As long as your contribution is your own, the background setting may, and usually should, reference the work of others -- as long as it's clear where you are borrowing from, borrow freely.
    – tripleee
    Commented Mar 4, 2016 at 15:09

If you feel that you are copying too much from "standard" sources (in your subfield), chances are you are. Keep in mind that your audience is mostly people in your field (generally), they should be familiar with the area. Just cite (the best/a few) reference(s), give the result you need (for benefit of somebody from outside the field stumbling on your thesis, or as a reminder to others), and move on.

Most of the "underlying theory" discussion should be more or less contained in the chapter on state of the art anyway. There detailed discussion of what has been done, were it fell short or left problems open is the bread and butter, and will be spiked with copious references.


This is a totally normal...ish :)

Once upon a time, scientists were almost universally humble, and for a person to single-handedly contributing even a speck of new information to the body of information that humanity had accumulated over millennia was considered quite the achievement.

As Charles H. Duell, Commissioner of US patent office in 1899 famously said:

"Everything that can be invented has been invented."

It is only in recent times (but still before you and I were born) that the notion of a "rockstar-scientist" existed. Before that, Scientists were typically wealthy noblemen who dabbled in Science because they didn't need to work for a living. So the idea of doing science as a profession also wasn't really anything like it is these days.

So why do you feel like you are plagiarising the work of others when setting the scene in your PhD thesis? Speaking from my experience of currently writing a PhD Thesis in Biology, it may be because you are internally conflicted that on the one hand we are but little cogs in a big engine; yet on the other, if we don't make ourselfs out to be the biggest/bestest cog ever, we fear we'll be replaced by ones that are.

Yet the format of a thesis has not changed in centuries - and perhaps that's a good thing :)

  • 3
    I don't think the OP is actually worried about "plagarizing", but that someone else could see it and accuse him/her of plagarism. In the witch hunt atmosphere that seems to prevail these days, you don't have to be guilty, just an accusation is enough to cause problems.
    – jamesqf
    Commented Mar 1, 2016 at 4:55
  • @jamesqf, that's a pretty good diagnosis :-)
    – trolle3000
    Commented Mar 4, 2016 at 16:03
  • Totally agree jamesqf - but the issue there is not the witch-hunting itself per se, it's the OPs perception that someone will actually call them out on it. While all the other answers give advice on not plagerizing, like the number 1 answer of "try to remember everything", what i'm saying here is that it's all in his head. He needs to worry less when he's doing nothing wrong :) Commented Mar 4, 2016 at 16:35

David Richerby's answer is a good one. In addition, you can make it more your own by adding some commentary. How do the theoretical tools that you are using compare with others that have been proposed? What are their weaknesses? What are the alternatives? Why have you chosen these particular tools for your particular problem?


These are similar questions any researcher faces while writing articles/ publications/ thesis. But what I feel different is the perspective of looking the problem. Maybe everyone's trying to solve the same thing now and then. Certainly, there are many contributions which have lead us to pursue the field you are in today. We indeed have to cite adequately as the future researchers would see the origins of our work. This is also establishing yourself in the field you are working along with established contributors.

What matters most is the following:

  1. How do you show the problem/How did you see the problem?
  2. Your perspective to tackle the issue with all necessary tools. You should clearly put your ideas to work for connecting all the dots.

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