Faith is a powerful thing, able to change lives. However its whims are unknown as most things.
Perhaps it’s the gods who manifest in strange ways, maybe man creates it as we do CO2. Maybe it’s just a type of element or matter, maybe it’s nothing and I’m just crazy.
Faith as I believe it works like matter, cannot be created or destroyed. Therefore our faith and beliefs go somewhere when we die. Hence ghosts.
Spirits manifest in many ways, as our traditional ghosts, strange energy, uneasiness, and figures in your peripherals, etc etc. Most mean no harm or even have a stable form. When we believe in ghosts we are effectively shaping this used faith & giving it a stable form. That also applies the other way around, don’t believe in ghosts? They won’t manifest because your organized, focused, and stabled faith over powers it.
Now sometimes a persons faith can be so powerful and strong that it will manifest on its own. These are often very strongly minded and strongly emotional people, often its hateful people but not the majority. Hence a lot of modern day religions, strongly spiritual people whose faith has spread long past their time for good or bad.
Only by belief in faith in things can we truly change, believe in nothing and you will get nothing.