According to Walpola Rahula, in his book, What the Buddha Taught (1962), he explains that nirvana is realized by the ‘being’ composed of the Five Aggregates who has gone out (p. 42). This is kind of an odd description. Let me back up so you can see the passage in question which is quite confusing.
“Here is should be clearly and distinctly understood, without any confusion, that what is compared to a flame or a fire gone out is not Nirvana, but the ‘being’ composed of the Five Aggregates who realized Nirvana” (p. 42).
We observe from Rahula’s words that the ability to realize nirvana is solely through the 'being' composed of the Five Aggregates, or the same, the psychophysical body made up of five constituents, namely, material shape, feeling, perception, volitions, and consciousness. This is the being who will realize nirvana. This is Rahula's version of nirvana which is Theravadin. (This aggregated being is also Mara the Buddhist devil! Why Rahula, or any Theravidin overlooks this important fact is beyond my ability to speculate.)
Moving forward, can such a being as Rahula’s being realize nirvana, who is composed of the Five Aggregates? The answer has to be in the negative.
Beginning from here, we have to ask, what can we learn about a being composed of the Five Aggregates from the discourses of the Buddha? First of all, as a being, I am form (or material shape), feeling, perception and consciousness that means that this is what I am. I am not beyond the aggregates or less than each of them. However, according to the Buddha this is identity view (sakkâyaditthi) which means the aggregates are the being or individual. With regard to each aggregate I regard them as my self. In the Identity View Sutta (Sakkâyaditthi Sutta) it states:
“When there is form, bhikkhus, by clinging to form, by adhering to form, identity view arises. When there is feeling ... perception ... volitional formations ... consciousness, by clinging to consciousness, by adhering to consciousness, identity view arises” (S. iii. 185).
Somewhat ironic, identity view is also wrong view as noted in the discourse before it which is the Micchâditthi Sutta. This idea of identity carries with it, by implication, a limitation: One cannot uncling from the Five Aggregates since one is composed, as Rahula claims, of the Five Aggregates! Again, ironic, neither the Buddha nor his disciples identify with the Five Aggregates. Only worldlings (puthujjana) believe they are the Five Aggregates. In fact, it is they who produce the aggregates according to the Dutiyagaddulabaddha Sutta.
“So too, when the uninstructed worldling produces anything, it is only form that he produces; only feeling that he produces, only perception that he produces; only volitional formations that he produces; only consciousness that he produces” (S. iii. 152).
While the worldling is a being who is composed of the Five Aggregates—or imagines he is—neither the Buddha nor his disciples (ariyasavaka) will have anything to do with them! In numerous discourses, the Buddha when regarding the Five Aggregates says, “This is not mine, I am not this, this is not my self” (M. i.136). But still more interesting is this passage.
“Whatever is there of material shape, feeling, perception, the habitual tendencies, consciousness—he beholds these things as impermanent, suffering, as a disease, an impostume, a dart, a misfortune, an affliction, as other, as decay, empty, not-self. He turns his mind from these things [MA. iii. 146], and when he has turned his mind from these things he focuses his mind on the deathless element thinking: ‘This is the real, this the excellent, that is to say the tranquilizing of all the activities, the casting out of all clinging, the destruction of craving, dispassion, stopping, nibbana [nirvana]” (M. i. 435–436, trans. I.B. Horner). (Brackets are mine.)
Apparently, the composed aggregated being who has realized Rahula’s Nirvana and gone out, is not the Buddha or his disciples since they’ve turned their minds away from the misfortunes of the Five Aggregates long before they are destroyed at death. Truth be told, there is nothing in the discourses of the Buddha that tells us about a khandha-being (i.e., aggregate-being) who realized nirvana. The Five Aggregates do not realize nirvana; they do not take refuge; they cannot distinguish between what is the path and what is not the path. They are incapable of discerning a Buddha from a worldling. The list goes on.