It is quite easy to understand what is a dhatu with this sketch and these definitions & notes. And particularly what a dhammadhatu is (as in SN 14.1/7-10 & SN 41.2).
Dhātus might be considered as graspable constituted elements making up a particular phenomena (e.g. an external ayatana, or even a whole world) - or just a primordial element (e.g. water).
They are grounded manifestations of some kind.
“Grounded”, in the philosophical meaning of being somewhat actualized; as the external sensory fields/grounds (ayatanani) are actualized through the fields of sensory experience.
Dhatus also belong to the later non-sensory worlds (loka).
For instance, (on the provided sketch,) dhammadhatu is the result (actualisation) of the mental manifestation of the immaterial khandhas, in the namarupa nidana (the nama part). The grounded dhatu is the dhamma as external field of sensory experience (bahira ayatana) -a mental phenomena.
Note that in the last note provided above, a dhathu is usually preceded by some kind of desire. There is usually a desire attached to it. Which might not be the case for a dhamma.
A dhatu might just be a desirably graspable dhamma. While a dhamma is just being a causally conditioned phenomena, originating from the khandhas.
“He (the Sambuddha) then taught me the Dhamma:
Aggregates, field of sensory experience, and elements”.
So me dhammamadesesi,
khandhāyatanadhātuyo
SN 8.12
And please Coëmgenu, you are a very smart young lad. Why are you trying to make Mahayana the prominent school.
What we are trying here is to find the common denominator of all early schools.
A non-schismatic original Buddhism.
I don’t really see myself as doing that. In fact, in the above OP and related discussion, I contrasted the prospective EBT-derived sense of dharmadhātu with the later Mahāyāna usage of the term.
If anything, perhaps it is you who are the crypto-Yogācārin.
Let try to make it a little less “crypto”, with my favorite example. The Picasso’s painting.
Get my little sketch handy.
As I said in my note, and at the end of my last post, dhatu is a dhamma that is desired, in some way.
So, to make it even simpler, let say that you went to see an exhibition, with the desire to see some Picasso paintings.
You stop before one of the painting.
There is a descent of namarupa (see the sketch) - Here it is not a tree, but Picasso’s painting. The material dhamma’s part. And the immaterial dhamma’s part, are Picasso’s khandhas.
But this is not what “hits” you.
What really hits you, (what is actualised) is this total dhamma that grounds itself on the external sensory fields of experience (bahirani ayatanani) ) - in this case the form of the painting, and the immaterial khandhas of Picasso.
Because this constituted manifested dhamma is graspable by you, and was desired, it is called a dhatu.
Now read the provided extracts. You will see this desire looming everywhere.
Whatever be the many desires and delights that are always attached to the manifold elements,
The longings sprung from the root of unknowing.
SN 7.18
As for the great multitude that follows my jaw-dropping insight with awe - and who share exclusively with me, the invaluable and mighty secret of my bank account number in the Bahamas; they’ll understand.
