Hi, everyone. I'm a new PhD student at a major research university. I'm looking for advice from professional historians about something that I feel silly asking my advisers: how "original" does my dissertation have to be? I'm finding the whole idea of making an "original contribution" a bit daunting. I mean, do I have to shoot for a topic that no one has ever written about before? Is it all right to tackle a historical topic/question that has been asked before in hopes of finding a new angle?
You shouldn't take it quite as literal. Your goal should be to add a meaningful contribution to academical discourse. It really doesn't have to be a topic which has not yet been studied. You just have to build on historiography and try to add something new. That "something new" could just aswell be a very refreshing and convincing take on a popular question. In theory, it could be easier to do research on a fairly unknown subject simply because it will be more difficult for anyone to challenge your claims. If you decide on researching a very well-known issue, there will be more blowback and it might be more difficult to convince those who are evaluating your final product. I wouldn't let that stop me though, if you are planning on doing a PhD on a certain subject and spending many years of study on it, you should be confident in your academical prowess to be able to defend your final product no matter how known the issue is.
My advice would be to go for something which really interests you. That could be a gap in historiographical knowledge or an issue you think deserves reevaluation. Also, don't be afraid to talk to your advisers about this, we've all struggled with the same question. Good luck!
One example of something new. There are two current major books in my field--The Whore's Story, which deals with 1700-1800, and Governing Pleasures, which deals with 1857-1900. No one studied or wrote about (in detail) the 50 years leading up to the 1857 Obscene Publications Act. So for my thesis I just joined their two books, did research into the Act, and figured out how it went from one to the other, and what developments helped it.
It should be original in some way or another. A new angle on an old topic might be just fine, but that new angle has to come from somewhere. Is it the application of a new methodology or theoretical approach to a set of sources that gives a novel reading of them? Is it a new set of sources altogether that causes the need for the reevaluation of old sources? The topic doesn't necessarily need to be original, but what you have to say does. Your advisors will know your specific topic and situation better than we can. There is no shame in broaching the topic with them. Helping their graduate students come up with a suitable project is part of what they are there to do.
You'll likely work with your advisor on your topic, and it's likely to change/become refined as you do more reading, preliminary research, and ultimately even your dissertation research itself can cause you to rethink some fundamental assumptions you had when you wrote your proposal.