The term “western philosophy” refers to the philosophical tradition that began in ancient Greece with the pre-Socratic philosophers and, later, with Socrates. Western philosophy began with a realization that the religious beliefs of the time, in Greek mythology, were well-founded and did not provide adequate answers to life’s fundamental questions.
The study of western philosophy has since developed. It is what is generally meant by “philosophy” at most western universities, though many include the study of eastern traditions. Philosophy has not lived in the west in isolation from religion, but is generally meant to be seperate affair, interacting with religion with respect to meta-religious and metaphysical questions, either enforcing or disputing religion (depending on the beliefs of the philosopher).
In general, there are four main eras that are traditionally studied in Western philosophy. The Ancient era begins around 585 BCE in ancient Greece, and ends with the spread of Christianity. There begins the Medieval period, during the middle ages in which philosophy’s focus turned towards supporting religious teachings, especially the existence and nature of God. This period leads into the Modern period, at a time in which natural science was maturing and new philosophical questions began to appear, sometimes challenging religious beliefs. The modern period was, in a sense, a rebirth of philosophy and led into contemporary philosophy that has been studied since the early twentieth century.