The question raised in the commentary is whether the space element is the same as the unconditioned dharma of space; and whether all consciousness is the consciousness element.28a-b. Cavities are called the space element; it is, one says, light and darkness.
If I understand correctly, the space element is defined by the absence of perceptible matter. I don’t think – and correct me if I’m wrong – that what is being defined here is two different kinds of space element, it’s all space, it just appears in two different ways.(Commentary) The cavity of the door, the window etc. is the external space element; the cavity of the mouth, the nose etc., is the internal space element.
…the void of the space element is light or darkness – that is to say, a certain type of color of matter … being by its nature light or darkness, the void will be day or night.
Impure in this context means not part of the path of liberation, productive of karma.28c. The consciousness element is an impure consciousness.
I’m not sure we’ve had a definition given of ‘arising’ yet. I checked in the earlier notes but didn’t find one. But the meaning is well-understood, and the commentary goes on to explain that arising is of the mind of living sentient beings; and that pure dharmas are opposed to arising. So far, so good. But then the commentary has this conclusion:(Commentary) Why is it not called pure? Because these six dhatus are:
28d. The support of arising.
So the pure mental consciousness, meaning the third and fourth noble truths (I think?), is not part of the consciousness element.Thus the five sense consciousnesses, which are always impure, and the mental consciousness when it is impure, give us the consciousness element.
It feels at this point that the text is tying up some loose ends. We now get to why so much time has been spent on analysing and categorizing rupadhatu:
There are three forms of striking enumerated in the commentary. The first is the common meaning of physical contact. The second is contact with an organ, for instance, the eye, with its sphere of action. The third kind is the striking of the mind with its object.29a-b. Only rupadhatu is visible (out of the eighteen dhatus)
29b-c. The ten dhatus which are exclusively material are capable of being struck.
The commentary then explains the difference between the sphere of action and the object of a sense organ. The discussion at this point is quite long, but it seems to be fairly intuitive. The sphere of action is the full extent of what the organ can perceive, and the object it perceives is within that field.
Since the next section gets into the moral value of the dhatus, this seems like a good place to stop for now.