There are a number of philosophical questions surrounding plagiarism. Obviously, taking someone else's ideas and championing them as your own ought to be punishable. But what constitutes this theft? Surely, a verbatim rip-off. But few professional plagiarists are that transparent. They, instead, paraphrase the ideas.

Perhaps, in certain circumstances, it is obvious when an idea has been paraphrased. But does an idea I paraphrased from an introductory class in the philosophy of mind constitute plagiarism? I hope not, for then learning would be impossible, and every academic could be held accountable for their crimes. This is because there is a causal story which relates every piece of propositional knowledge I have to some particular individual; ex nihilo fit. Do they need to be cited in my academic work? OK. But they were just transferring something they learned from someone else, and so on, ad infinitum. Do I need to cite a piece of common knowledge known to all specialists in my area? What if I acquired that meme in the beginning half of a published article?

The point I am trying to make is that it is no trivial matter determining whether someone has plagiarised or not. There is a certainly a lot of conceptual work to be done here.