Writing the Statement of Purpose

A statement of purpose for a science PhD program is nothing like the essays one might write for college, medical school, or undergraduate scholarships. Those essays can read more like entries for a personality contest, where the implicit objective is to try to look like a sparklier snowflake than the other applicants. For a science PhD application, the statement should focus more on your ideas than you.

Female Science Professor (a.k.a. FSP) has written two fantastic essays (here and here) on what a statement of purpose should and should not look like. She has reviewed hundreds of statements and is a tenured professor, whereas I've seen only a few dozen and am a postdoc. Weight our advice appropriately.

The core of my advice is captured by FSP's statement that

I don't believe that the depth of your love for science, or any pursuit, correlates with how early you discovered that love, so I find such descriptions of childhood inspiration unconvincing in an application for graduate study in the sciences.

There is no need to make it sound like you've been fated to go into science, do research, or develop novel nonparametric methods to study Arctic sand mites. There's no set path to becoming a scientist. If you haven't seen it already, you'll notice that many successful professors haven't had "linear" careers, though nonlinearity is more common in some fields than others.

Similarly, don't argue that the fact that you got an A+ in ReallyHardUpperLevelScienceCourse, scored perfectly on a standardized test, or had an IQ of 155 at age 10 means you're qualified to be a scientist. (I've seen the last one, though the numbers have been changed to protect the naïve.) First, your recent grades and scores will speak for themselves, and only your parents continue to find your childhood adorable. Second, the argument suggests a belief that scientists are born more than they are made. It's far better to describe how you've pushed yourself to learn particular skills--a talent required for a sustainable research career--than to say that you're smart. One could argue that the A students in particular need to show that they can push themselves, make mistakes, and learn.

The statement should mostly be about the ideas in the field that interest you and questions you'd like to investigate. It's fine to reference particularly germane papers that excite you (do not simply cite the most classic papers in the field that were assigned reading in undergrad), but you do not need to spell out a fixed plan of research for the next five years or cite for the sake of citing. Describing interesting questions in several thematically related areas is fine. Briefly describe how your past experiences have prepared you for research, and briefly discuss what attracts you to this particular program. That's it!

The writing should be extremely clear, but it does not need to be cute or clever. The quality of your writing matters; no adviser likes rewriting students' draft manuscripts. In my opinion, the sine qua non of writing advice remains Strunk & White's Elements of Style. I suspect every native English speaker either loves that book or has been conditioned through repeated exposures to ignore it; I wonder how many non-native English speakers know it and find it helpful. Working to improve your writing now is just win all around.

There's not much to sweat, really.