Śivasaṃhitā 1.48

Superimposition (adhyāsa) as the mechanism of cosmic illusion. Everything that exists in time—past and future—and in space—that which has form and that which does not—is projected onto the immutable background of Spirit. This background is not modified by the projections, as a screen is not affected by the images that traverse it.

The compound mūrtāmūrtam (the formed and the formless) is exhaustive: not only the gross and visible is included in the superimposition, but also subtle, mental, and spiritual states. Yadbhūtaṃ yacca bhāvyaṃ (what was and what will be) extends the projection across all time. Nothing escapes the screen of the Supreme.

The concept of adhyāsa is the starting point of Śaṅkara’s Brahmasūtra-bhāṣya, which defines it as the apprehension of one thing as if it were another. The Śivasaṃhitā applies this concept on a cosmic scale: the entire universe is adhyāsa onto the Paramātman. The practice of yoga is the process of apavāda, the progressive negation of superimpositions.