Religion is a taxon for sets of social practices characterized by belief and ritual behavior. The term was originally applied to Judaism, Christianity, Islam, Hinduism, Buddhism and Confucianism, the so-called “world” religions, but it has since come to be used of a broader class, including forms of life that do not have these names but that have distinctive beliefs or ceremonies, common to a geographical area or to some group of people. The study of different religions, then, is often comparative, and the notion of a “true” or “really existing” religion has gained traction among some scholars.
In the nineteenth century, some philosophers developed a new approach to the concept of religion. They abandoned the traditional assumption that religion involves belief in a particular kind of reality, and they sought to understand the phenomena of different religions without judging them normatively or comparing them to one another. This approach, which came to be known as phenomenology, has become a central method of the philosophy of religion.
This phenomenological approach has led to the rejection of the notion that there is a universally valid set of beliefs about God and the afterlife, and to the development of theories that allow for the existence of religious phenomena in cultures that do not have explicit metaphysics or belief in disembodied spirits. It has also enabled scholars to study religions as historical formations, in their own terms and as they are practiced by their adherents.
The most basic definition of religion is that it is a system of beliefs and ritual behaviors in which man recognizes his dependence on, and hopes for help from, the mysterious, superhuman Deity (or deities). It is this deeply felt need that gives religion its raison d’être. The recognition of this need is accompanied by the persuasion on the part of man that he can bring himself into friendly communion with the Deity and find therein all good and happiness.
Religions are organized around the observance of special days, such as the full moon and the new moon, recurring natural events, such as the seasons and the annual cycle of planting and harvesting, the two solstices, and astronomical events, such as eclipses. Various rites of sacrifice and purification are associated with these events. Certain places, made venerable by the presence of reputed visions or oracles, come to be regarded as especially holy, and are therefore dedicated for worship.
The most important work of the twentieth century in the philosophy of religion has been done by Continental philosophers such as Martin Heidegger, Jean-Paul Sartre and Simone de Beauvoir. In addition, many of the philosophers who belong to the analytic tradition have also addressed questions of religious significance, such as A.N. Whitehead, Bertrand Russell and G.E. Moore. In the 21st century, however, a number of people who do not consider themselves religious have developed important ideas about the nature and importance of religion. This has given rise to a school of thought sometimes called naturalism or secular humanism.