Taking into account the following points from Lal and another previous comment:
-Viññāna means “without ñāna” or without wisdom:
-Viññāna also means “defiled consciousness”;
-vi = defiled, nana = wisdom (vinnana)
-It is understood that the vinnana of an Arahant is pure or undefiled.
-when one attains the Arahanthood, one will have “undefiled or pure consciousness”.
So vinnana means:
-Without wisdom
-Defiled consciousness
-Yet an Arahant is the embodiment of wisdom.
-Yet an Arahant has undefiled consciousness.
So how can an Arahant have vinnana?
To say an Arahant has vinnana, is equivalent to saying:
-Arahant is without wisdom
-Arahant has defiled consciousness
“Vinnana of an Arahant” is a contradiction. Like saying dry water.
For example:
If vinnana is defiled consciousness, it can be compared to a dirty cloth.
An anariya’s vinnana(dirty cloth) is unclean.
To say an Arahant’s vinnana is “undefiled” is like saying: an Arahant’s dirty cloth is clean.
To me the following would make more sense:
-An anariya’s consciousness is vinnana.
-An Arahant’s consciousness is just nana(minus the vi).
-Goal of purifying the mind would be to eventually change one’s vinnana to nana.
-An anariya’s consciousness is defiled. Without wisdom. Anariyas do not experience things as they are, not see true nature of reality. Rather an anariya labels experiences as the following 3 ways:
1) good because they like it based on lobha. Generate amisa sukha vedana.
2) bad because they dislike it based on dosa. Generate amisa dukha vedana.
3) neutral. neither like nor dislike based on moha(delusion, a defilement). Generate
amisa upekkha.
-An Arahant’s consciousness is undefiled. If they have only nana rather than vinnana that means with wisdom(because nana means wisdom). They know the true nature of reality. They do not label experiences as “good/bad/neutral based on moha”, but they experience things as they are, see things as neutral, but their neutrality is different from that of an anariya in that an Arahant’s neutrality is not based on moha. Their neutrality is niramisa upekkha vedana, based on wisdom from their pure undefiled minds.