A Ph.D. in religion prepares you to become a member of the clergy, but can also be a strong background for a liberal arts career -- writing about the intersection of religion and society, teaching religious studies at the college level or serving as religious consultants for business and government entities. There's no "right" major for pursuing a Ph.D. in religion; you can get into a religion program with a variety of academic backgrounds.
A degree in religious studies gives you a broad background in world religions. You'll learn about religious traditions, their evolution and the ways in which religion affects society. Depending upon the school you choose, your major might be called either religion or religious studies. If you're interested in a particular religion, you might choose to concentrate in classes related to that religion. Some schools also offer majors relevant to a specific religion. The University of Chicago, for example, offers a major in Buddhist studies.
Philosophy and religion are inextricably linked, and many philosophers have weighed in on religious questions. Philosophy can help you develop the critical thinking skills you need to pursue graduate studies in religion. You'll learn about how approaches to religion have evolved over generations and gain insight into the thoughts great thinkers throughout time have had about religion. Classes in philosophy of religion and courses that focus on specific religious philosophers -- such as Aquinas or Augustine -- can further prepare you for graduate school.
If you're interested in how religion affects society and how society affects religion, a sociology degree could be ideal. You'll learn about how religions evolve and affect cultural norms and group behavior. This degree can be ideal if you're interested in understanding the interactions between religion and society rather than mastering specific theologies. Focus on taking classes on the sociology of religion to get the most informed background.
A major in theology helps you gain insight into a specific religion's theology or a specific group of religion's theologies. You might major in Christian theology, for example, or pursue a degree in theology at a religious school. Marquette University, for example, offers a teaching-focused degree in Catholic theology. If you're contemplating becoming a member of the clergy or want to focus on a specific religion as part of your Ph.D. program, a theology major might be appropriate.