“This world, Kaccāna, usually leans upon a duality: upon (the belief in) existence or non-existence…. Avoiding these two extremes, the Perfect One shows the doctrine in the middle: Dependent on ignorance are kamma-formations…. By the cessation of ignorance, kamma-formations cease….” (SN 12:15)

The above saying of the Buddha speaks of the duality of existence (atthitā) and non-existence (natthitā). These two terms refer to the theories of eternalism (sassata-diṭṭhi) and annihilationism (uccheda-diṭṭhi), the basic misconceptions of actuality that in various forms repeatedly reappear in the history of human thought.
Eternalism is the belief in a permanent substance or entity, whether conceived as a multitude of individual souls or selves, created or not, as a monistic world-soul, a deity of any description, or a combination of any of this notions. Annihilationism, on the other hand, asserts the temporary existence of separate selves or personalities, which are entirely destroyed or di