Reduction of the cognitive experience
If one continues the reduction of experience beyond this point, the gradual reduction of the cognitive experience begins. This reduction of the cognitive experience is also a case of letting go of the former level of cognition. Each progressive level is a letting go, or an absence of the former level of experience, or a stopping of mental activity. This cognitive reduction also takes four steps as follows:
(1) The realm of infinite space (akāsanantāyatana) – the objects perceived (rūpa) are absent.
(2) The realm of infinite perception (viññānañcāyatana) – attention is focused on the process of perception.
(3) The realm of nothing (akincaññāyatana) – the attention is withdrawn from the process of perception and focused on nothing.
(4) The realm of neither sensation nor no sensation (neva saññā nāsaññāyatana) – the attention is withdrawn even from the awareness of nothing. Therefore the attention is not focused on any sensation,though not remaining totally unconscious. This is being at the threshold of consciousness.
The above four levels of experience are levels of cognitive reduction. The two teachers of the Bodhisatta, Alara Kalama and Uddaka Rama Putta, had both reached only the realm of nothing (akincāññayatana). It was Uddaka Rama, the teacher of the second teacher, who had entered the realm of neither sensation nor no sensation (neva saññā na asaññāyatana). The Bodhisatta learned from the second teacher how to reach that state and did reach that state himself. Yet he wanted to go further but there was no one to teach him how.
This was why the Bodhisatta decided to join the five ascetics and practice asceticism. He practiced asceticism to the ultimate level. He fasted till he became almost a skeleton, and even tried to stop breathing until he fell unconscious and people thought he was dead.