Correspondence is the relationship between a natural thing and its spiritual meaning, and it exists according to that thing's use. The spiritual world and the natural world correspond; forms exist here because their purpose exists there. Sacred text such as in the Bible has outward form and inner meaning and the two are in complete correspondence.
This can be illustrated by the following example: when you see someone you love, you smile. It seems like a pretty simple process, but in reality, it's not; instead it’s a whole string of events, with simpler things relating to more complex ones, rising to the spiritual level and coming back down. First light bounces off that person’s face and enters your eyes. Your eyes send information to your brain. From there it passes into your mind - a spiritual organ, according to Swedenborg’s works - and registers in your consciousness. You recognize the person and feel love for them! But that has to get translated back down through the brain, which generates signals to all the facial muscles, which then contract or relax according to orders, producing a smile.
As you can see, the real activity here is mental. You “see” that face in your mind; before then it’s just a string of impulses carrying information. And you “smile” in your mind, with the information translated back into more impulses carry more information leading to physical activity. Your eyes don’t “know” what they’re seeing; your cheeks don’t “know” that they are smiling. They are simply projections of an internal, spiritual thing - your mind - into a lower physical reality.
That’s an example of correspondences, on a very small scale. What you see on the natural plane of existence corresponds to your idea of what you see and the affection you have for it. Your reaction in turn corresponds to the affection you have. The correspondence of one with the other is a way for the more important spiritual reality - the activity in your mind - to project itself into physical reality.
Swedenborg’s works tell us that those correspondences are more important than we could possibly imagine. In fact, everything in the physical world corresponds to something in the spiritual world. Mountains, for example, are not just mountains; they are the spiritual love of the Lord projected into physical reality in the form of mountains. Trees are rooted, lasting spiritual principles projected into physical reality in the forms of trees. A river is a flow of true spiritual ideas projected into physical reality. In a way, it’s like the spiritual world is one huge collective mind, expressing itself through physical reality the way our own minds express themselves through our own bodies.
And then there’s another level: Swedenborg’s works say that the most perfect form of spiritual reality, heaven, is in a state of complete, all-encompassing correspondence with the Lord, with each aspect of heaven expressing some aspect of the deepest reality of all, which is the Lord’s love and wisdom themselves. This is way out at the raw edge of what we can grasp, but it’s really quite beautiful. Spiritual reality is not part of the Lord, but it is from the Lord and can express the Lord as it approaches perfection. Physical reality is not part of the Lord and is not part of spiritual reality, but it is from the Lord by way of spiritual reality, and it can express spiritual reality (and thus the Lord) as it approaches perfection.
This is why the Lord had so many physical laws for the children of Israel: the prescribed physical actions corresponded to spiritual meanings, which in turn corresponded to aspects of the Lord Himself. It explains why we see advanced astronomy and awareness of nature in the remnants of ancient religions worldwide: They came from the Ancient Church, which had a surpassing knowledge of correspondences and used that knowledge in worship and life. To some degree it explains why we still love mountaintops, beautiful gardens, natural beauties like waterfalls: we can still feel the spiritual reality close inside them, even if we don’t know it in its specifics.
Correspondences also explain the continuing power of the Bible even in this skeptical age. The Lord provided that it should be written - most of it, anyway - in correspondences, which actually give access to His whole infinite being. We may not understand them, but that does not limit their power to teach us, to form our minds; this is why it’s important for people to read the Bible with open minds, to let the Lord enter in.
One other fascinating and meaningful aspect of correspondences comes in the form of what Swedenborg’s works call the “Grand Man” or “Grand Human.” Because heaven is in complete correspondence with the Lord and the Lord is the ultimate, infinite, divine and archetypal human, this means that heaven is in human form. And this is quite literal and precise: parts of heaven correspond the heart, others to the lungs, others to the brain, skin, ears, hair, digestive tract, everything. What’s more, just as the body’s organs are broken down into tissues and the tissues into cells, so also is the Grand Human broken down. So as an individual angel you might serve a brain function for a cell that performs a protective function for an organ that plays a digestive role in the Grand Human. That sounds a bit strange, but if you consider the unique mix of ideas and affections in each of us you can see how we could, indeed, fill such precise roles calling for such precise degrees of precisely layered talents.
And since physical reality is in correspondence with spiritual reality, this means that our communities and societies in this world are also in the human form, though obviously not all to a very perfected degree. This also sounds strange, but it’s an interesting exercise to think about the functions of the brain (to think and judge), the skin (to protect and hold together), the lungs (to draw in new thoughts and ideas), the digestive tract (to create energy to do work), heart (to circulate energy and ideas) and muscles (to do the actual work) and relate them to the functions of human organizations. Most likely, effective human organizations will indeed have these elements, and will have them in the proper balance.
Finally, of course, correspondences are one of the primary reasons for this website to exist. Our purpose is to share the knowledge of correspondences offered through Swedenborg’s works, so we can all understand the Bible, the Lord and ourselves a little bit better and find our own places in the Grand Human.