What is the gift of the shaman? It’s the ability to receive sensory input from our non-physical senses. Everyone has a spirit sense, but not everyone can be aware of it.
Our brains have spent our entire lives focused exclusively upon the sensory input from our body. It’s like having a tool in your garage that you never use. Even if someone told you that you have it, you still have no idea where it’s kept.
What is the benefit of perceiving things that are outside of our physical senses? If I can’t possibly see it with my eyes, then it really has no impact upon me, right? Yes and no. There are many things that exist that our physical senses cannot detect: gasses in the air, magnetic fields, radiation from the sun, etc. Science has allowed us to build devices that can detect these things, but it hasn’t yet quantified spirit.
Do the inhabitants of the spirit world commonly do harm to those of us existing in the physical world? No, I do not believe that to be true. Can the entities in the spirit world have an effect upon us? I believe yes.
To understand the actions of free willed beings, we need to have some insight into their motives. Most spirit beings do not concern themselves with us, much like we do not concern ourselves with them. To put it into physical world perspective, most of us do not worry about what fishes do, or the creatures that live beneath the dirt or those that fly high above us. Our world is on the surface and that is where we typically exist.
The physical layers above and below us are there, but have little impact upon our day to day actions. However, this doesn’t mean the inhabitants cannot affect or influence us.
A shaman is aware of the things that live in different layers of being. This allows them to observe and communicate with the inhabitants there for the purpose of guidance and healing of others in their community / tribe.