Shloka 18
Adhyāya 353 — Kathā-prāmāṇya (Authority of Transmission) and the Brāhmaṇa’s Ascetic Resolve
द्रष्टा द्रष्टव्यं श्राविता श्रवणीयं ज्ञाताज्ञेयं सगुणं निर्गुणं च यद् वै प्रोक्ते तात सम्यक् प्रधान नित्यं चैतच्छाश्वूतं चाव्ययं च
drašṭā draṣṭavyaṁ śrāvitā śravaṇīyaṁ jñātājñeyaṁ saguṇaṁ nirguṇaṁ ca yad vai prokte tāta samyak pradhānaṁ nityaṁ caitac chāśvataṁ cāvyayaṁ ca
毗湿摩言：彼同一实在，既是见者，亦是所见；既是令闻者，亦是所闻；既是知者，亦是所知；且既具诸德相，亦超越诸德相。孩子啊，所谓正当称为“普拉达那”（Pradhāna，原初本原）者，实即此补卢沙。此理常住、永恒、不坏。
पितामह उवाच
Educational Q&A
The verse teaches the all-encompassing nature of the highest Reality: it is simultaneously subject and object (seer/seen, knower/known), and it transcends the opposition of saguṇa and nirguṇa. It further identifies what is called Pradhāna with Puruṣa, emphasizing an ultimate, eternal, imperishable principle underlying all experience.
In Śānti Parva, Bhīṣma (lying on the bed of arrows) instructs Yudhiṣṭhira on dharma and liberation. Here he shifts to a metaphysical exposition, describing the supreme principle in comprehensive terms and reconciling philosophical categories (Pradhāna/Puruṣa; saguṇa/nirguṇa) to guide the listener toward liberating understanding.