But is nirvana as understood by a Buddhist identical to death as understood by a materialist? That is, does nirvana=annihilation?
In Śrāvakayāna the idea of nirupadhiśeṣa-nirvāṇa is understood as cessation of the skandhas and this mass of suffering.
But again, how is then that Buddhas -- Amitabha, for example -- can inhabit Pure Lands and teach innumerable beings? Have such Buddhas somehow failed to achieve nirupadhiśeṣa-nirvāṇa?
To answer this requires clarification on the general ideas on nirvāṇa as they differ between the Śrāvakayāna and Mahāyāna.
A Buddha in the Sthavira-Śrāvakayāna context achieves cessation of all suffering, which entails an end to their skandhas and psycho-physical continuum at death, thus the "end of this mass of suffering". When an arhat dies their psycho-physical continuum ceases entirely and they are not to reappear again in any of the three realms.
In the Mahāsāṃghika-Śrāvakayāna context the Buddha represented something more transcendental and omni-present, but until the appearance of the Mahāyāna, which arouse from within the Mahāsāṃghika school, it seems such transcendence was not really understood. Emulation and reproduction of it was also likewise not understood. This is why nirvāṇa came to be "revealed" or "demonstrated" for the sake of beings, but in reality there was no "being" that achieved cessation of suffering, but a transcendental force at work for the sake of beings. Let me refer to Venerable Guang Xing's work entitled The Concept of the Buddha
The Mahāsāṃghikas’ religious philosophy was based more on faith than on reason, and accepted whatever was said by the Buddha or, more precisely, whatever was taught in the Nikāyas and the Āgamas. As a result, they developed the concept of a transcendental (lokottara) Buddha based on the superhuman qualities of the Buddha, as discussed in Chapter 1 above. Two aspects of the Mahāsāṃghikas’ concept of the Buddha can be identified: the true Buddha who is omniscient and omnipotent, and the manifested forms through which he liberates sentient beings with skilful means. Shakyamuni was considered but one of these forms. The true Buddha supports the manifested forms that can appear in the worlds of the ten directions. In Mahayana Buddhism, the former aspect – the true Buddha – was developed and divided into the concept of the dharmakāya and the concept of the sambhogakāya; the latter aspect – the manifested forms – was developed into the concept of nirmaṇakāya. Thus, the Mahāsāṃghikas are the originators of the idea of the nirmaṇakāya, and the manifested forms can have many embodiments. Furthermore, they also introduced the theory of numerous Buddhas existing in other worlds. (p53)
Again, from this perspective there is no being that really achieves nirupadhiśeṣa-nirvāṇa. It is all a display for the benefit of beings by a transcendental force that was not as clearly defined as it would be in later times by the Mahāyāna.
Nevertheless, they still maintained the goal of arhatship as outlined by Śākyamuni Buddha, which like their colleagues in the Sthavira meant cessation of one's psycho-physical continuum and in turn all of one's subjective sense of suffering and agency. In other words, nirupadhiśeṣa-nirvāṇa meant one could no longer interact with reality anymore as all sense of agency and subjectivity would terminate with the skandhas.
Buddhas in the Mahāyāna context are not beings (sattva
) anymore. There is omniscience, but not individuated existence as an identifiable continuum. As it is said in the Vimalakīrti Nirdeśa Sūtra
one pays homage "to you who stand nowhere like infinite space". This means that they do not really inhabit or abide anywhere. It is all an appearance for the benefit of beings.
There is no point of reference that can be identified in terms of the dharmakāya. To say buddhas exist is misleading, but on the other hand it cannot be said at the conventional level buddhas do not exist at all. They are force among beings and continue to interact with reality, but without volition, karma or even conception of beings to be liberated. As it is said in various scriptures a bodhisattva that conceives of beings to aid and liberate is no real bodhisattva. This is all the more so when it comes to buddhas.
This is because with prajñā there are no objects to be discerned. In discerned objects there is no real prajñā. Furthermore, there is no perception of beings as such a perception is a result of afflictions and faculties, all of which a buddha does not possess.
Amitābha and other manifest buddhas (nirmaṇakāya) are effectively unreal illusions perceived by beings. They are a result of the past immeasurable stores of merit accumulated from the infinite past and aspirations. Thus their manifestation is not specifically willed, but a result of the force of their merit. In the case of a buddha where there is no longer agency or identity, how could there be a willed determination to even teach beings?
This is why Amitābha Buddha inhabiting a pure land and teaching beings is a convenient arrangement brought about through the collective wholesome karma of beings meeting with the aspirational force of a buddha, but such a perception is effectively only operational from the side of the beings, not that of the buddha in question which ultimately abides nowhere like infinite space.