tad-anusandhāya yaḥ paśyet bhūteṣu parama-ātmanam īśānam sarva-bhūtānāṃ tam evaṃ viduḥ amṛtaḥ

tad (that) anusandhāya (having searched) yaḥ (who) bhūteṣu (in all beings) parama-ātmanam (Supreme Self) īśānam (the Lord) sarva-bhūtānāṃ (of all beings) tam (Him) evaṃ (thus) viduḥ (knows) amṛtaḥ (is immortal)

Advaita Vedānta (Ādi Śaṅkarācārya): This verse, as interpreted by Shankara, underscores the non-dualistic philosophy of Advaita Vedanta. The Supreme Self (Paramātman) is seen as the ruler (Īśānam) of all beings, implying that the ultimate reality is the same in all entities. Shankara's commentary on the Taittiriya Upanishad (2.1.1) is relevant here, where he establishes the identity of the individual self (ātman) with the universal Self (Brahman) through the mahāvākya 'tat tvam asi' (you are that). In the context of this Praśnopaniṣad verse, recognizing the Supreme Self in all beings leads to the realization of the brahman-ātman identity, culminating in liberation (amṛtaḥ). This is in line with Shankara's emphasis on the importance of self-inquiry (anvēṣaṇam) in realizing the ultimate truth. Thus, the verse points to the path of knowledge (jñāna yoga) as the means to attain immortality, not in the physical sense, but in the sense of transcending the cycle of birth and death through the realization of one's true, unchanging nature.

Vaiṣṇava tradition (Rāmānujācārya / Madhvācārya): From a Vaiṣṇava perspective, this verse highlights the devotional path to realizing the Supreme Lord (Paramātman) who is the ruler of all beings. Rāmānujācārya, in his Śrī Bhāṣya, emphasizes the concept of 'śeṣa-śeṣi-bhāva,' where the individual selves (jīvas) are always under the control of the Supreme Lord (Īśvara). This verse is seen as an exhortation to contemplate the omnipresence of the Lord, leading to a deeper devotional relationship between the jīva and Īśvara. The attainment of immortality (amṛtaḥ) is interpreted as achieving a state of eternal service to the Lord, which is the ultimate goal of the Vaiṣṇava tradition. Madhvācārya, in his commentary on the Brahma Sutras, further elaborates on the distinction between the Lord and the individual selves, emphasizing the need for devotion and surrender to realize one's true nature and attain liberation. Thus, this verse is understood within the framework of bhakti yoga, where love and devotion to the Supreme Lord are the means to attain spiritual liberation.

Neo-Vedānta (Swami Vivekānanda / S. Rādhākrishnan): Swami Vivekananda, in his lectures on the Upanishads, brings out the practical and universal implications of this verse. He emphasizes that seeing the Supreme Self in all beings is not just a philosophical concept but a practical reality that can be experienced. This, he argues, leads to a sense of oneness with all existence, which is the basis of compassion, empathy, and service to humanity. In his writing 'The Complete Works of Swami Vivekananda,' he notes that the realization of the Divine in every being is what leads to true immortality - not just in the sense of individual liberation but in living a life that transcends the boundaries of the ego and serves the greater good. Similarly, S. Radhakrishnan, in his philosophical works, interprets this verse as pointing to the universal values of tolerance, understanding, and the inherent dignity of all human beings. He sees the pursuit of spiritual knowledge and the realization of the Supreme Self as a journey that enriches human life and society, leading to a more harmonious and peaceful world. Thus, this verse is connected to contemporary life by emphasizing the importance of spiritual values in achieving personal and societal transformation.

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