Geoff:
To paraphrase Ven. Ñāṇananda, it's not that an arahant gets
half of nibbāna upon awakening, and the other half when s/he dies.
Upon awakening they have already "gone out," they are "cool," and
they have reached "the end." Even parinibbāna can be used to refer
to a living arahant.
The dhamma isn't about some sort of thanatos desire to attain
completion in the grave. It's about realizing "the end" here and
now.
Geoff:
I think that there are numerous sutta references to the awakened
mind which explain what is not the foundation of an arahant's
experience. Firstly, by way of training: The seen is merely the
seen (diṭṭhamatta). The heard is merely the heard (sutamatta). The
sensed is merely the sensed (mutamatta). The known is merely the
known (viññātamatta). Ud 1.10 Bāhiya Sutta:
Secondly, the absence of specific fabrication (abhisaṅkharoti) or
volitional intention (abhisañcetayati) towards either existence or
non-existence. MN 140 Dhātuvibhaṅga Sutta:
Cf. Ven. Ñāṇananda, Nibbāna
Sermon 04:
And Nibbāna Sermon 06:
And thirdly, consciousness which is unestablished (appatiṭṭha
viññāṇa). SN 22.53 Upaya Sutta:
As for the qualm that this last passage refers to the death of an
arahant, the phrase: "Unexcited, he personally attains complete
nibbāna. He discerns that, 'Birth is ended, the holy life
fulfilled, done is what had to be done, there is nothing further
here,'" is the standard paricope referring to the time of
awakening, i.e. a statement of the attainment of arahant fruition
(e.g. DN 15, MN 105, etc.), and not the time of death of an
arahant.
The above passages referring to the cognition of an arahant are
succinctly presented in AN 4.24 Kāḷakārāma Sutta:
Ven. Ñāṇananda considered the Kāḷakārāma Sutta important enough to
write a text on it.
All the best,
Geoff