You've downloaded all the necessary documents: the recommendation forms, the application, the sheet on which you are to chart every relationship you've ever had with anyone in the entire world who has gone to a college or university or other institute of higher education that has any loose affiliation whatsoever with the one to which you are applying—that sort of thing. And you've written your personal statement (likely title: "Why I Am The Perfect Candidate For Admission To Your Graduate Program In Nuclear Physics: A Brief Primer On The Particle Accelerator I Built In My Parents' Basement For The Fifth Grade Science Fair"). But now comes the hard part: the scholarly essay.
Many Ph.D. programs require their applicants to write a reasonably lengthy essay on a topic relevant to the subject they wish to study. The assumption is that, in order to successfully engage in doctoral-level study, a student must already possess a certain amount of knowledge about the field. This essay, then, is your chance to show the admission committee that you truly are ready to engage in the kind of high-level critical inquiry that constitutes doctoral study, and that you will, upon completion of your course work and dissertation, make enough of a contribution to that field to justify the time and effort you spent on your studies, as well as the time the faculty spent on their teaching.
The question, then, is this: should your essay be written on a topic that is already the subject of much critical investigation, or should it be on a more esoteric aspect of your field?
The simple and rather unfortunate answer is that it depends on what you are hoping to accomplish. Both options offer benefits and drawbacks. Primarily, it depends on where your own strengths and weaknesses lie and what you want the essay to demonstrate about you.
Let's say you're trying to decide on an essay topic for the Ph.D. program in Near Eastern Studies at Princeton University. You are fascinated by the political culture of Saudi Arabia, as well as how the al-Saud family's relationship with the Wahhabi branch of Islam has affected their relationship with their people and with the Western world. Is this a good topic? Remember, the issue here is not whether you will sound intelligent - arguably, everyone who is applying to this program will be on the bright side. And you should assume that everyone hoping to be admitted will share a certain basic level of knowledge on the major issues shaping the Near East. So before you decide that this is the right topic, you should ask yourself several questions:
1. Are other candidates likely to write about a similar subject?
2. Will I be able to develop any new and previously unconsidered insights?
3. Is my knowledge and understanding of this topic likely to be seen as extraordinary in the eyes of the professors who will read the essay?
How you answer any one of these questions is likely to affect the way you consider the other two. If, for example, you do decide to write on this topic, you should be aware that other applicants are likely to submit similar essays. The topic, after all, is not so esoteric or original that others are unlikely to ever have considered it. In fact, it has been the subject of more than a few books over the past several years. But that doesn't mean that you should not persevere: If you are confident that you will bring a fresh and thought-provoking perspective to the issue, then by all means go for it.
Even if you have not engaged in any original research yourself - one of the reasons, after all, that you are ostensibly applying to a Ph.D. program is to learn how to do that kind of investigative work in the first place—you may nonetheless have an original take on the issue based on your extensive reading on the subject. If that is the case, then write about it. But if your essay will likely consist of little more than rehashings of previously-developed ideas, then it is probably not the right topic for you. Remember, the reputation of the university is on the line here, and the expectation is that, once you have matriculated, you will begin a long and fruitful career defined by original scholarship and paradigm-shifting writings. Your scholarly essay (Princeton, for the sake of accuracy, refers to it as a "writing sample") should demonstrate that potential.
Some people, on the other hand, might choose to write about an aspect of their field of study that has not been the subject of massive amounts of scholarly inquiry. An applicant for the Ph.D. program in Slavic Languages and Literatures at Harvard University, for example, might eschew writing about, say, religious humanism in Tolstoy's major novels, and choose instead to expound on the South American literary antecedents to the magical realism in Bohumil Hrabal's fiction. In making a decision like this, the applicant signals his willingness to delve into areas of his field for which there is no overwhelmingly large body of work from which to draw. And if that applicant is subsequently able to develop original and creative insights, then his chances of impressing the professors on the admissions committee become that much greater.
The bottom line is that your decision should be based on your own particular set of skills. It may sound obvious, but the subject about which you choose to write your scholarly essay, and the way you go about the writing itself, can have a very real impact on your chances of being admitted to the program or programs you desire. Either way, as long as you explore the topic you've chosen in as much detail as you can, and write about it in a way that is both thought-provoking and original, then you will have done all you could to maximize your chances for admission.