Once, the Arcanum was composed of only three orders—the black of life and joy, the grey of balance, and the white of death and ends. Only in the last few decades have others been added, to reduce the ranks of Apostates and better reflect the spectrum of morality and use, rather than a simplistic trinary. Thus, the red of honor and war and the blue of history and knowledge.
The hedge witches are not under the aegis of the Arcanum as their magic is beneath the notice of sorcery. And the divine theurgists remain apart with their own, unique powers that are not sorcery. Thus, neither is incorporated into the Order system.
The Orders were created by the founders of the Arcanum for the purpose of easing administration of all sorcerers around the world. The Orders were also, initially, a means of dealing with the philosophical differences between sorcerers. Over time, the Orders developed into the social, legal, and political centers of the Arcanum. In the early days, the Orders were ensured great leeway in their conduct of internal affairs. Even with the expanded ability to handle their own operations, they must remain within the bounds of Arcanum law and restrictions. Thus, the White Order is a more “acceptable evil” versus most of the Apostates.
As part of their duty to the Arcanum, the three elder Orders each maintain a school, all at different parts of the world. Every school allows students from the younger Orders, and allied elder Orders—ex. the Black Order allows Grey, Red, and Blue Orders; the Grey Order allows all Orders. The younger Orders have been pursuing attempts to set up their own schools, almost since they were created. To date, they have received very little support from the Council.
In order to best fit their evolving purpose, every Order has a unique place for its members around the world. Access to the Order houses is limited to members of the Order itself. These are the core social and political centers of the Orders, places members can do their own activities with others like themselves. As such, the Orders form the backbone of the Arcanum in ways that no other element of sorcerous society and government can.