A few evenings back someone asked me about my feelings towards religion. Being very well-studied on the religions of the world, and a spiritual person to boot, I naturally have some opinions. I took the opportunity then to organize my thoughts and wrote down some notes on the subject.
Religions generally follow the same structure. My belief is that these commonalities exist because religion serves a common need within the human psyche and our minds have only limited ability to put context around certain concepts. These are sweeping generalizations that will be offensive to many because of their distillatory effect. If you care to continue, an open mind is best. I am in no way meaning to disparage or be offensive in any of the examples I will use. I merely picked religions that emphasized the specific points I wished to make. Quite frankly, I think all the religions have something to offer and strive not to be judgmental but rather analytical. Comments are of course, always welcome.
The core of any religion is the External Reality. This can be an entity or a force, it can be classified as spiritual, or physical, or natural, or combinatory. The only consistency is that it encompasses all of that which we perceive as outside our personal reality. It is something bigger than ourselves, and may include ourselves. It may be passive, or active, anthropomorphic or completely unknowable. In every case, the central element is that reality which is external to us as individuals.
There must then be a Personal Context relative to that External Reality. This again might be an orientation (I'm part of the universe!) or a positional (I serve my God!) or simply subjective (You are all living in my dream!). Explain it anyway you like, each religion has a way of making sense of the difference between you and me and other. The simplest might be that we're all the same, it is only time that allows our matter or energy to be different. More complicated might be that we are ants under the foot of cosmic deity. You get the idea.
When you know the players, then you need the Relationship. These are the rules or guidelines for how the players are connected or interact. Some structures are highly organized with commandments, edicts, punishments, etc. (Perform these rituals! Follow these commandments!) Others are simple and focus on personal attainment or just the essence of being (You need to be open to the universe!). This is usually what most people think about as the difference between religion and spirituality.
When we examine where your world-view becomes your religion, we start with the Responsibility to Share. The simplest of these are just a desire to educate those around us with the amazing enlightenment that we've achieved through blah, blah. The more complicated are the crusaders with mandates to convert the masses. When you stop constraining your beliefs to your own behaviors or morality it ceases to be a world-view and becomes religion. Again, this is my over-simplification and probably misappropriation of labels for the purposes of this discussion.
Lastly, a religious structure always has some form of Exclusivity. Obviously, if it were just a world view we wouldn't need to share it with others, it would just be the principles of how we exist in the world. When it becomes something we believe should influence others, it becomes a religion. This brings with it the notion that it isn't for everybody, or that somehow an adherence to the Relationship is a prerequisite to alignment within the structure. There are simple forms of this (You just aren't enlightened!) and complicated forms of this (Don't eat with the infidels! Unbelievers go to hell!).
When you distill the concepts of the world religions down to these subject areas, it becomes easy to view the overlaps and commonalities. Once you have a dictionary (or lexicon for the technically minded) we have a means to compare and contrast. More importantly we can make the case that the specifics of the religion become irrelevant for the formation and appreciation of spirituality. Much like cultures that share common roots but hold to their vehement differences we can say the same thing using different words and argue ad nauseum about why we disagree.
When it comes to education, these commonalities work to our advantage. Essentially, an immature mind while unable to appreciate many of the nuances that the observant use to separate religions can certain grasp the basics of almost any religion. As they develop within a particular religion they are learning the nature of spirituality, and how to identify and exercise their faith and morality. As they mature, they can hopefully learn to minimize the exclusionist principles of their specific religion and embrace a more universal aspect of their own spirituality and moral context. Naturally, the more exclusionist the religion, the harder this is for the individual. For example, look how hard it can be to leave a cult, or the penalties for ceasing to be Muslim.
The limiting factors for personal spiritual development are typically the strength of their own sense of self and the extent their self-image is supported by the religion or exclusionist principles. Consider a woman raised in a traditionally male-centric religion such as Mormonism. It can be hard to establish their own spiritual identity in a more universal way because of the mindset in which their self-image is more reliant on a male influence.
No discussion would be complete without addressing the concept of atheism. Essentially, this world-view is a lack of awareness or acceptance of the first principle (that being there exists a reality external to oneself). Intellectually this shows a fundamental immaturity in personal development and a basic self-centeredness that leads to unpredictable and therefore flawed reasoning. The ability to acknowledge a reality outside of oneself is foundational to any discussion of morality or relationships.
In the end, you wind up in a religion because of how you were raised, or what reinforces your personal world-view. Once you learn to embrace the commonalities with other religions it opens to the door to much better understanding of their world-views. Often this is the key to getting in touch with your own sense of self.
Good luck with that.