I have a big problem and I need your opinions and your advices.

Someone did his PHD 4 years ago using data collected over 10 years to develop some equations and simulate them. I re-measured the same data 2 years ago (i.e. spanning over 12 years; the methods of collecting the data are different) and I want to develop equations with simulating them in different program (I will do the programming of it). One of the equations was developed by him, and the two others are different. Is it ethical to continue my thesis or not? Is it considered as plagiarism? I have cited his results in the Scientific Background section, and in the Discussion I will compare it with my results.

  • 2
    Similar to this question, there is no ethical problem, provided you cite the older work and make clear what's new and what isn't in your work. The only concern is whether your improvements/additions are substantial enough on their own to earn you a PhD.
    – user37208
    Jul 14, 2018 at 19:11
  • It is not an ethical/ plagiarism problem, it is an originality problem. Ask yourself if your results enough new to be interesting.
    – Greg
    Jul 15, 2018 at 5:13
  • It's ethical, but the real problem is that it might not get you a PhD.
    – xuq01
    Jul 15, 2018 at 11:22

2 Answers 2


It doesn't sound like there's an ethical problem here -- as long as you appropriately credit the earlier work. (That is, prominently cite the prior work and clearly explain the relationship.)

However, you should note that re-doing someone else's work with minor changes will generally be viewed as less significant and novel than the original work. In particular, doing almost the same analysis as someone else's PhD thesis is likely not sufficient for another PhD.

That said, it is valuable (and often publishable) to re-do prior work. This is helpful to you and the community, and could form part of your PhD.

  • 2
    One should add: It is often a necessary part of a PhD to redo the work of those who gone before you, in order to get sufficiently acquainted with the methods and their inherent problems, before you can contribute with something novel.
    – nabla
    Jul 14, 2018 at 19:39

Your concerns are a bit misplaced, though you should have concerns. Plagiarism is using other people's words and maybe ideas without attribution. Speaking "their words as if they were your own."

Copyright comes in to play when using other people's words, of course, though copyright law is a mess and varies from place to place. But if you quote and attribute the earlier work appropriately you won't be in the wrong here.

But note that copyright applies to words (pictures,...), not to ideas. While I can't publish images of Mickey Mouse, I can certainly discuss the "idea" of Mickey Mouse without ethical or legal concerns.

Patent law is a bit different and allows the exclusive use of "ideas" of certain kinds for a fixed period. But that doesn't apply here.

However, to have an acceptable dissertation, you need to do something that is considered novel by (at least) those who review it at your university. Simply repeating earlier work isn't new, though it may be that you use new techniques, or come to a different conclusion. Some research can invalidate older work, and, especially when it uses better techniques than the original, is certainly valid and worth publishing.

If what you do is truly different then you have the basis for a dissertation. If it is a little bit different, you probably don't. But ethics would only be involved if you copy and present the copy as your own.

It may be an apocryphal story, but Picasso is said to have said "Good artists borrow. Great artists steal." The same sort of thing has been said of "writers", "physicists", etc. But in the case of art, no one would accuse Picasso of presenting the work of another as his own, though he did steal ideas from other artists.

Build your work on the ideas of others. But make it clear what is yours and what is "theirs."

However, another problem that might apply here is the problem of parallel work. If you work in parallel with someone else but don't know that until late in your studies, you may wind up in a situation in which your work must be discarded. There have been exceptions to this, but they are rare. If you didn't know, but should have known, you are just out of luck. However, it has happened that dissertations have been submitted by people unknown to each other more or less simultaneously. This will generally cause, at least, an investigation. That doesn't seem to be the case here, but you may be in a situation in which the other person just reached the finish line first.

The reason for that is that "ideas are free" and what I can learn, you can learn. The thoughts I can have, you can also have. The insights might be shared, etc. But if you are a bit quicker to the end than me, then you have a dissertation and I don't. Not especially frequent, but it happens.

  • Thank you for your comments but I should and must explain something, the previous work dealt with the topic using data from two countries.My work is restricted with one country and honestly I heard with his thesis just last year but I found differences sufficient to continue but I am still worrying about that.When I sent my PhD proposal I did not know at all that someone did similar work. Jul 14, 2018 at 20:14
  • Your advisor is your best source. Make sure that he/she has all the facts. It will be bad if you can't continue, but you may be able to salvage something even from a bad situation, though it will likely cost you time. You don't need to say it, but your advisor bears some responsibility for knowing these things, so, I hope, has an incentive to make it work out.
    – Buffy
    Jul 14, 2018 at 20:17

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