The Natural Order

The Natural Order, or Just Is for short, is one of the, if not the only, governing forces behind the universe. One of its most important roles, is that it is connected to the flow of life and death and assures that people live and die as they should.

Description
The Natural Order or what is usually called Just Is is a powerful and unknown factor of the universe. It is impartial and is unknown how long it has existed, if it didn't already always exist. The earliest form of the Order, is in regard to the demanded existence of both Darkness and Light. The existence of The Empty is also necessitated by the Order, but little else is known about this mysterious realm besides the being in charge of maintaining the realm's immutability.

Notable Beings

 * Reapers have a connection to it. They can see a person's whole lifetime and when and how that person will die and when it is time for them to die. The Natural Order is impartial and both good and evil are subject to its power and when it is time to die, a person will and must die.
 * Death has a role in his job as Death. He follows the natural order as it dictates the flow of life and death. Death while able to bend or even break the order, didn't like to do so. As they often cause chaos and violations in the world. As he asked Dean when he was Death, "Wrecking the natural order's not quite such fun when you have to mop up the mess, is it?"
 * Eve is also aware of the Order and claims to have an "arrangement" between the balance of killing between humans and monsters.
 * Atropos, one of the Fates, has a role within the Natural Order. She designs the ways in which people die, and makes sure that events occur according to destiny.
 * Mandatory Existence of Light and Dark - God and The Darkness are the most notable pillars of The Order, as they both need each other to exist; otherwise, reality itself would be erased. However, it has been speculated by Sam that if both were to be killed, reality would continue to exist in a new state.
 * The Cosmic Entity, having predated everything including The Darkness, God, and creation also has role seemingly demanded by the Natural Order. While information on The Empty, the realm the Cosmic Entity is beholden to, is relatively scarce, the Entity must maintain its status quo at all times to be at peace as evident by the intense pain he endured when Castiel impossibly woke up from his eternal slumber and his dire efforts to either return Castiel to sleep or throw him out, whichever method returned matters back to constancy.

Notable Places
The Natural Order also have places, that fall under its laws. Mostly the spiritual realms where souls go. Reapers are the ones that take humans souls to Heaven, Hell, and possibly monster souls to Purgatory.
 * Heaven: The spiritual world where mostly good souls go to.
 * Hell: The spiritual world where mostly evil souls go to.
 * Purgatory: The spiritual world that souls of monsters go to.
 * The Empty: The void predating Creation where angels and demons are sent upon death. Believed to be impossible to be recovered from, except if the Empty’s inhabitant the Cosmic Entity expels someone.

Trivia

 * In Bobby Singer's Guide to Hunting, Eve herself wanted to ensure that her children also follow the Natural Order, even going to extremes as forging the dragon swords to stop her dragons, should they attempt to destroy other beings.
 * In the same book, Lethe or Oblivion, a pagan deity, was also shown working for Heaven. Her role was to wipe memories of people who have seen or witnessed something supernatural that they shouldn't have.
 * During Dean's time as a demon, he states that his kind are part of The Natural Order and that's how it was set up.
 * In situations where the Natural Order is disrupted (e.g.: a person dying before/after their time, or a person being resurrected), the aftermath will last as long as the cause of the disruption exists. As Tessa once mentioned after Dean (during his day as Death) refused to reap a little girl, "chaos and sadness will follow her for the rest of her life" (referring to the girl). According to Death, Sam and Dean, due to their repeated resurrections, "cause disruption on a global scale".
 * The Natural Order appears to be the laws that govern the totality of existence.