Shloka 40
मनु-उपदेशः — भूत-उत्पत्ति, इन्द्रिय-निवृत्ति, तथा पर-स्वभाव-विवेकः
Manu’s Instruction on Elemental Origination, Sense-Withdrawal, and Discrimination of the Supreme Nature
पृथग्भूतौ प्रकृत्या तौ सम्प्रयुक्तौ च सर्वदा । यथा मत्स्यो जलं॑ चैव सम्प्रयुक्तो तथैव तौ
pṛthagbhūtau prakṛtyā tau samprayuktau ca sarvadā | yathā matsyo jalaṃ caiva samprayukto tathaiva tau ||
毗湿摩阐明：二者虽以本性而别，却恒常相合。正如鱼与水为两种实体，却在生存经验中不可分离；同样，自我（ātman）与内在器官如智（buddhi）在本质上有别，却在具身经验中共同运作。
भीष्म उवाच
Educational Q&A
The verse teaches discernment: the self (ātman) and intellect/mind (buddhi) are inherently distinct, yet in embodied life they operate in constant conjunction. Recognizing this helps one act in dharma without mistaking mental functions for the true self.
In Śānti Parva, Bhīṣma is instructing Yudhiṣṭhira on philosophical and ethical foundations after the war. Here he uses the fish-and-water analogy to clarify how two different principles can remain inseparably associated in lived experience.