This dissertation explores conflicts between religion and medicine, cases in which cultural and religious beliefs motivate requests for inappropriate treatment or the cessation of treatment, requests that violate the standard of care. I call such requests M-requests (miracle or martyr requests). I argue that current approaches fail to accord proper respect to patients who make such requests. Sometimes they are too permissive, honoring M-requests when they should not; other times they are too strict. I propose a phronesis-based approach to decide (...) whether to honor an M-request or whether religious beliefs are medically valid. This approach is culturally sensitive, takes religious beliefs seriously, and holds them to a high ethical standard. This approach uses a principle of belief evaluation developed by Linda Zagzebski: The Principle of Rational Belief, which is founded upon Aristotelian virtue ethics. In addition to the Principle, I propose a concrete set of conditions to assist caregivers in clinical case evaluations. In the final chapters, I apply the phronesis-based approach to well-known adult cases such as the refusal of blood transfusions by Jehovah’s Witnesses and requests for continued (futile) care by Orthodox Jews at the end of life. Also, I consider cases involving children such as African female circumcision and cases of faith healing. I argue that The Principle of Rational Belief should define the threshold of the kinds of M-requests for children that can be honored, but I allow a lower threshold for M-requests made by competent adult patients. (shrink)