Why do we dream?

1. The experience of dreaming exerts a perennial fascination. Why do we dream? I can only speculate. 

Scientists have no agreed-upon explanation. If you're a physicalist, then the question is what if, any, biological function dreams have. If you're Darwinian, then you seek an evolutionary explanation. 

But what about from a Christian dualist perspective? 

2. Perhaps the question of why we dream is related in part to the question of why we play. Dreams are the mind at play. Maybe the mind requires a certain amount of daily unstructured time to retain sanity. 

3. In addition, dreams are a witness to the existence of the immaterial soul. Although the dreamer is embodied, a sleeper in bed, yet within the world of the dream it's a sensory world without physicality. So a theological function of dreams may be to remind us that reality isn't confined to bodies or physical experience. Dreams are an emblem of personal existence that survives the dissolution of the body. We can leave the body behind but still take a lot with us. In that respect, dreams are a bridge between this life and the afterlife. A token of the intermediate state. 

They can help us from becoming too attached to this life and this world. Too fearful to let go. They provide something to step into. Material existence isn't the sum total of reality. There's something ahead as well as behind. 

4. In addition, dreams can link us to dead relatives. I'm not saying that as a rule, the dead actually visit us in dreams. Generally, I'd say the encounter is imaginary, based on memory. But it reminds us of those who've gone before. It keeps them fresh in our memories. And that, too, may be a psychological bridge. We're on one side while they are on the other side, but dreams form a symbolic window. Although we're separated by the river of death, we can see each other standing on the riverbanks, awaiting reunion. 

5. Then there are supernatural dreams. God sometimes uses the medium of dreams to communicate. Or he may give permission for a sainted relative to make contact if the dreamer is undergoing a crisis and needs some timely encouragement. 

Conversely, there can be supernatural nightmares that shake unbelievers out of their spiritual complacency. In addition, I presume that those who dabble in witchcraft may open a terrifying door, where evil spirits haunt them in nightmares.