The process of discovering the final substratum (adhiṣṭhāna) involves three progressive steps: First, understanding that an untrained mind sees projected reality (like silver on shell) while scientific observation ends at physical forms (atoms/particles), requiring śabda-pramāṇa (which comes from Īśvara and can't be contradicted) to go further; Second, recognizing knowledge-power (Īśvara) by observing intelligence at every level of creation (quarks to atoms to forms); Third, realizing that even Intelligence requires Awareness (can't think without it), leading to the understanding that through satya-mithya analysis, forms are less real than atoms, atoms less real than Īśvara, and Īśvara less real than pure Awareness – resulting in an objective vision that sees form, intelligence and Awareness simultaneously, which when fully assimilated becomes one's own vision (mokṣa).

Additionally, Īśvara serves as both efficient cause (nimitta-kāraṇa) and material cause (upādāna-kāraṇa) of the universe. Unlike a pot-maker (efficient cause) who needs clay (material cause), Īśvara must be both causes because: (1) as maker, Īśvara must have knowledge-power of everything (sarvasya kartā sarvajña), and (2) as material, Īśvara can't use pre-existing material (would lead to infinite regression). Therefore, Īśvara pervades every form while remaining free of what it manifests, like ocean and its bubbles – making Īśvara‘s “material” pure intelligence rather than any physical substance.

See complete program by Andre Vas at: https://www.yesvedanta.com/atma-bodha/