Vertical cosmology
In the vertical cosmology, the universe exists of many worlds (lokāḥ) – one might say "planes" – stacked one upon the next in layers.
Each world corresponds to a
mental state or a
state of being.
A world is not, however, a location so much as it is the beings which compose it; it is sustained by their karma and if the beings in a world all die or disappear, the world disappears too.
Likewise, a world comes into existence
when the first being is born into it.
The physical separation is not so important as the difference in mental state;
Humans and animals, though they partially share the same physical environments, still belong to different worlds because their minds perceive and react to those environments differently.
The vertical cosmology is divided into
thirty-one planes of existence.
The planes are divided into
three realms, or dhātus, each corresponding to a different type of mentality.
These three (Tridhātu) are
- the Ārūpyadhātu,
- the Rūpadhātu, and
- the Kāmadhātu.
The latter comprises the "
five or six realms".
In some instances all of the beings born in the
Ārūpyadhātu and the Rūpadhātu are informally classified as
"gods" or "deities" (devāḥ), along with
the gods of the Kāmadhātu,.
The deities of the Kāmadhātu differ more from those of the Ārūpyadhātu than they do from humans.
It is to be understood that
deva is an imprecise term referring to any being living in a longer-lived and generally
more blissful state than humans.
Most of them
are not "gods" in the common sense of the term, having little or no concern with the human world and rarely if ever interacting with it;
Only the lowest deities of the Kāmadhātu correspond to the gods described in many polytheistic religions.
The term "
brahmā" is used both as a name and as
a generic term for one of the higher devas.
In its broadest sense, it can refer to
any of the inhabitants of the Ārūpyadhātu and the Rūpadhātu.
In more restricted senses, it can refer to an inhabitant of one of the nine lower worlds of the Rūpadhātu, or in its
narrowest sense, to the three lowest worlds of the Rūpadhātu.
A large number of devas use the name "Brahmā", e.g. Brahmā Sahampati, Brahmā Sanatkumāra, Baka Brahmā, etc.
It is not always clear which world they belong to, although it must always be one of the worlds of the Rūpadhātu below the ¦uddhāvāsa worlds.