“When this is, this comes to be; with the arising of this, this arises; when this is not, this does not come to be, with the stopping of this, this is stopped.” — Vera Sutta (AN 10.92)
All the formulas of paṭicca-samuppāda are specific applications of this principle. When applied to the phenomena of our daily experience, this principle enables us to wean our minds from the tendency to rest on the concepts of existence and non-existence. As a preliminary step towards this end, those two concepts are replaced by the two terms uppāda (arising) and vaya (decay), These latter enable us to view the two extremes rightly (sammā diṭṭhi) as they are suggestive of conditionality. In developing samatha and vipassanā (calm and insight), the mind is made to oscillate between these two terms with ever-increasing momentum, spurred on by the three signata: anicca (transience), dukkha (suffering) and anattā (not-self). At the peak of intensity in this oscillation, the lingering notions of existence and non-existence wane into insignificance since the mind now hardly rests on them. The three signata involved in the oscillation have by now built up a powerful motive force of detachment. So the mind gets weary of (nibbidā) the extremes, and decides to step out (nissarana) of the process. Hence he cuts off the thread of selfhood—already made slender as at the stage of neither-perception-nor-non-perception (nevasaññānāsaññāyatana)—the thread by which his mind was oscillating under the artificial superstructure of concepts. As he lets go selfhood, he touches the realm of cessation (so nirodhaṃ phusati — Poṭṭhapāda Sutta). Thus the distressful tension abates (dukkhūpasama), the mental synergies are allayed (saṃkhārūpasama), and the triple process of conceptualization subsides (papañcavūpasama). Along with the concepts of the extremes, that of a middle also disappears. In short all concepts lose their significance for him (papañcasaṃkhā-pahāna). As for the relevance of the metaphor of mental pendulum that we have adopted in this connection, attention may now be drawn to the following passage of the Udāna dealing with the problem of Nibbāna:
“For him who clings, there is wavering, for him who clings not there is no wavering. Wavering not being, there is calm; calm being, there is no bending; bending not being, there is no coming and going; coming and going not being, there is no death and birth; death and birth not being, there is no ‘here’, no ‘yonder’, nor anything between the two. This indeed is the end of Ill.” — Catutthanibbānapaṭisaṃyutta Sutta (Ud 8.4)
The word nissita (lit., resting on) is reminiscent of the Buddha’s sermon to Kaccāyana on the two extremes. This being so, the rest of the passage accords well with the metaphor. To one who rests on the verbal dichotomy,there is mental unsteadiness or irritability. Hence to him who does not rest on it, there is no such irritability. The absence of irritability brings about tranquility of mind. The tranquil mind has no inclination towards conceptual distinctions of two extremes or of any middle position. This release from the bondage of concepts is itself the end of suffering.