Context

Sūtra 18 lists the specific upāyas — the means — for the madhyavikāsa described in sūtra 17. The closing -ādayaḥ ('and so on') marks the list as non-exhaustive: a set of exemplary entry points from which the practitioner draws, not a complete inventory.

Primary reading

The means, grouped: first, vikalpakṣaya — the dissolution of conceptual activity; second, śaktisaṃkoca and śaktivikāsa — the contraction and expansion of energy, whether as breath retention and release or as the alternation of introversion and extroversion of attention; third, vāhaccheda — the cessation of the breath-flows; fourth, ādi-anta-koṭi-nibhālana — sustained attention at the beginning and ending point of a breath, a perception, a thought. Each is a distinct door to the same madhya.

Commentarial layer

Kṣemarāja's commentary on this sūtra is dense with specific practice instruction, and he situates the listed means within the upāya hierarchy — āṇavopāya, śāktopāya, śāmbhavopāya — according to the degree of effort each involves. The fuller unpacking of his instructions awaits expansion from the primary source; what the sūtra itself establishes is the principle that multiple techniques, of differing subtlety, converge on the single expansion of the center.

Common misreadings

Reading the list as a sequential curriculum — these are multiple entry points, not stages to be completed in order. And treating vikalpakṣaya as suppression of thought: it is dissolution, not suppression. The difference is decisive — suppression uses effort to push thoughts away; dissolution is the natural subsidence of mental activity when attention rests in the ground.