The original work you produce as students at Princeton, including the third essay for this class, will have at minimum two distinct components: a stock-taking of existing thought relevant to the topic at hand, and some new contribution to that sphere of discourse.
Once you have identified and assimilated the body of sources that constitutes the context you're working within, you need to do two things to make sure that your own work is itself a solid, valuable source. The first is to very clearly distinguish between the preëxisting discourse that your work is engaging and your work itself. When these lines are not clearly drawn it can look like you have something to hide, and your reader may suspect one of three things. The first is that you’re just repackaging other people’s work and that there’s no original material there, and academic work needs to make some original contribution to justify its existence. The second is that you're blurring the lines between better established thought and your own novel claims in an effort to shield the latter from challenge and scrutiny. Thirdly, sloppy or inconsistent attribution may raise the suspicion that you're deliberately making it difficult for the reader to revisit your sources because you distort or otherwise misrepresent them in a way that promotes your own thesis. It has to be easy for your reader to see where the preëxisting intellectual exchange you're joining ends and your original contribution begins, and to access the sources you invoke as your work's context.
It also has to be easy for your reader to see that the sources you’ve used to inform your work are authoritative. Your reader should be able to easily identify the source of each piece of the preëxisting discourse you're referencing to context your own work. Your audience should never have to take your word for anything or wonder where your information is coming from and how authoritative it is or isn't. Any time you quote, paraphrase or refer to information from another source your work has to make this explicitly clear by attributing the information to that source in properly formatted citations that identify the source and allow the reader to easily locate that source. Then, if a reader has doubts about a particular element of the intellectual excahnge you’re engaging, or just wants to follow up and learn more about that element, your text makes it as easy as possible for them to do this. In your own research you'll likely find that secondary sources will make reference to other sources of interest for your project and, if the authors have followed established protocols for citation and bibliographic documentation, these references should make it easy for you to locate these sources yourself. It's important that you pay your own readers the same courtesy.
As students at a tier 1 research institution, you want any original work you do to be a worthy contribution to knowledge and something that has the potential to serve as valuable source material for other work. This means that you need to adhere to the academic codes and standards that are the foundation of the trust and confidence that allow for the constructive accumulation of knowledge. Another, more immediate, concern is the need to ensure that you don’t commit violations of the rules of academic integrity. This includes everything from copying work wholesale and submitting it as your own; to copying passages of other people’s work or paraphrasing other people’s work without attributing it; to deliberately inserting errors in citations to make it more difficult for the reader to access your sources. More detailed information is available in Academic Integrity at Princeton, available on the University Website. The Princeton University Library Website also has a directory of manuals and other resources for the most commonly used citation styles.