Thanks Anicca for the link.
I checked out MN49 and liked it very much. I also checked out DN11 and found this:
"'Your question should not be phrased in this way: Where do these four great elements — the earth property, the liquid property, the fire property, and the wind property — cease without remainder? Instead, it should be phrased like this:
Where do water, earth, fire, & wind have no footing?
Where are long & short, coarse & fine, fair & foul,name & form
brought to an end?
"'And the answer to that is:
Consciousness without feature, without end,luminous all around:
Here water, earth, fire, & wind have no footing.
Here long & short coarse & fine, fair & foul , name & form are all brought to an end.
With the cessation of [the activity of] consciousness each is here brought to an end.'"
Seems to me to be referring to the same thing as luminous mind.
From the commentary: "Another interpretation equates the luminosity of the mind with the "consciousness without feature," desribed as "luminous" in MN 49 and DN 11, but this interpretation also has problems. According to MN 49, that consciousness partakes of nothing in the describable world, not even the "Allness of the All," so how could it possibly be defiled?"
Also from the commentary: "A more reasonable approach to understanding the statement can be derived from taking it in context: the luminous mind is the mind that the meditator is trying to develop. To perceive its luminosity means understanding that defilements such as greed, aversion, or delusion are not intrinsic to its nature, are not a necessary part of awareness."
It would seem to me that if defilements are not intrinsic to the luminous mind (the mind the meditator is trying to develop), then it is possible that the luminous mind is the same as/part of/aspect of the "consciousness without feature." Therefore the so-called development of the mind is not really development but merely named as such.