Many people involved with the study of religion try to define it based upon its conceptual content. According to substantive and essentialist definitions, religion is characterized by some basic essence which is common to all religious systems, but not to any non-religious systems.
One of the most popular essentialist definitions today is based upon the notion of the sacred an idea introduced largely by the work of theologian Rudolf Otto with what he called the numinous. This was extended by the research of Mircea Eliade, who emphasized that the nature of religion could not be reduced beyond the difficult-to-define idea of the sacred. Daniel C. Maguire, Professor of Ethics in the Theology Department of Marquette University, defines the matter in his book Sacred Choices:
- Religion is the response to the sacred. So what is the sacred? The sacred is the superlative of precious. It is the word we use for that which is utterly and mysteriously precious in our experience. Since there is no one who finds nothing sacred, religion is all over the place.
There are a number of problems with substantive definitions such as this. Aside from the fact that the above ignores many of the critical aspects of religion which are addressed by functional definitions, it doesnt do much to really explain what the sacred is supposed to be. If all it amounts to is that which we value most highly, it doesnt distinguish religion from other beliefs and belief systems very well. Is a Yankees fan really religious in the same way that a Dominican monk is? That hardly seems fair to religion and doesnt seem to provide a good basis for learning about or understanding religions.
Other essentialist definitions are not quite so vague. An early definition comes from one of the first scholars of religion, E.B. Tylor. According to Tylor, religion can be defined simply as the belief in spiritual beings. Although the nature of what qualifies as spiritual may be a bit uncertain, this is still clearer than the notion of the sacred. Now, however, we have two new problems: not all systems which we might call religions necessarily include spiritual beings, and not everyone who believes in spiritual beings necessarily does so in the context of a religious system.
Finally, when we reduce religion to any one or even two features, we end up overlooking other attributes which are common to religious systems. If religion is reduced to the sacred or belief in spiritual beings, what about things like rituals or moral codes? Are they really so irrelevant? That doesnt sound very likely, but we can be misled into thinking it is true if convinced that there is a single essence which defines religious belief systems. Religion is more multi-dimensional than substantive definitions give it credit for.
Thus the basic problem with substantive definitions of religion is that when they are general enough to perhaps apply to all religions, they are too vague to be very useful and end up being applicable to belief systems or beliefs which just shouldnt be labeled religions. Once they are no longer too vague, however, they describe as essential to religion something which not all religions actually have and which is not alone in structuring religious beliefs.
If we accept a substantive definition of religion, we end up looking at religion as simply a type of philosophy, a system of bizarre beliefs, or perhaps just a primitive understanding of nature and reality. From the substantive or essentialist perspective, religion originated and survives as a speculative enterprise which is all about trying to understand ourselves or our world and really has nothing to do with our social or psychological lives.
Nevertheless, that does not mean that the concepts of the sacred or even of spiritual beings are not important to questions of religion substantive definitions may not be enough by themselves, but they do seem to have something relevant to tell us. Whether too vague or too specific, essentialist definitions still end up focusing on something very relevant to religious belief systems. A solid understanding of religion cannot be restricted to such a definition, but it should at least incorporate its insights and ideas.

