- The study of the fundamental nature of knowledge, reality, and existence, esp. when considered as an academic discipline.
- A set of views and theories of a particular philosopher concerning such study or an aspect of it.
- The belief in and worship of a superhuman controlling power, esp. a personal God or gods.
- Details of belief as taught or discussed.
Definitions never tell the whole story, but they are a start. If a philosophy is the study of the fundamental nature of reality and existence, and religion is belief in and worship of a superhuman controlling power, why do religions have philosophic underpinnings?
And if religion are the details of a particular belief system (perhaps one could even use the word "cosmology?") and philosophy is the set of a views of a particular belief system, where do you draw the line between them?
The most natural line is the advent of organization, or structure, or institutionalization, of the set of beliefs, but by that line, it seems to me that science and religion become hard to separate. (Don't crucify me, atheists, just bear with me for a moment.) The study and testing of structures and nature through scientific method is a particular practice of philosophy, since the scientific method is a set of philosophic principles of inquiry.
Further, we think of "organized" religion and other religions. For example, one of the attractions of paganism for many is that it's unorganized and highly individualistic. The appeal of many Eastern religions in the Western world (Buddhism, Taoism) also seems to stem largely from the individualized practice of religious principles, although most of that rests on some hefty misinterpretations. There are definitely temples and hierarchies for these religions we think of as "disorganized," and one can certainly develop a personal practice of any major religion, including Christianity or Islam if one wants to.
So without the line that is organization or institutionalization, where do we draw the line? And why? What's the difference between a set of beliefs about the world reasoned to and adhered to, and one presented externally and adhered to? Should we demand that each person reason their own beliefs? Doesn't that seem like reinventing the wheel over and over again?