Philosophy majors are not currently required to write a senior thesis. Nevertheless, there are advantages in writing a thesis. First, the effort provides a fitting “capstone” experience for the work you have put into the major. Second, it provides you with a solid writing sample to use in grad school applications, or to publish in an undergraduate journal. Third, you learn a lot.
What the thesis is. The senior thesis is a long paper (15-20 pages) on a particular problem or figure in philosophy. You read a lot on the subject, and work with a particular professor over the course of a semester in making your paper as good as it can be.
When you write it. The senior thesis should be among the last things you do in the philosophy major – so, sometime at or after the end of your junior year (or 75% done with your degree). If you are planning to use your thesis as a writing sample, keep in mind that many grad schools have application deadlines in December/January for the following academic year. So if you were hoping to attend grad school in Fall of 2020, you would want to work in your thesis in Spring or Fall of 2019.
How you set it up. Once you are about halfway or two-thirds done with your degree, you should ask yourself what so far has really fascinated you, and what you’d like to learn more about. Let’s call it X (free-will, eudaimonism, induction, etc.) Then you should approach a faculty member who knows a lot about X and is someone with whom you would like to work. Ask the faculty member if they’d like to serve as your senior thesis advisor. At that point you can work out the further logistical details – what semester to work on the thesis, how to get started reading about X, what specific thesis related to X you should think about, and so on. In the end you will sign up for a “Readings and Research” class (PHIL 4910) for 3 credits with that professor.
Questions? Feel free to ask any faculty member how the senior thesis works. And, if you are considering grad school in philosophy, you should also discuss this far in advance with a faculty member (be ready for a chilling tale of rejection rates and unfavorable odds). Going to grad school in philosophy, should one decide to do so, requires a lot of strategic planning.