तद्यथा महामत्स्य उभे कूलेऽनुसंचरति पूर्वं चापरं च, एवमेवायं पुरुष एतावुभावन्तावनुसंचरति स्वप्नान्तं च बुद्धान्तं च ॥ १८ ॥
tadyathā mahāmatsya ubhe kūle’nusaṃcarati pūrvaṃ cāparaṃ ca, evamevāyaṃ puruṣa etāvubhāvantāvanusaṃcarati svapnāntaṃ ca buddhāntaṃ ca || 18 ||
In support of the idea set forth above, the following illustration is being given: As in the world a great fish that moves freely, never being swayed by the river-currents, but rather stemming them, swims alternately to both the banks of a river, eastern and western. and while swimming between them, is not overpowered by the intervening current of water, so does this infinite being move to both these states—which are they?—the dream and waking states. The point of the illustration is that the body and organs, which are forms of death, together with their stimulating causes, desire and work, are the attributes of the non-self, and that the self is distinct from them. All this has already been exhaustively explained.
In the preceding paragraphs the self-luminous Ātman, which is different from the body and organs, has been stated to be distinct from desire and work, for it moves alternately to the three states. These relative attributes do not belong to it per se; its relative existence is only due to its limiting adjuncts, and is superimposed by ignorance; this has been stated to be the gist of the whole passage. There, however, the three states of waking, dream and profound sleep have been described separately—not shown together as a group. For instance, it has been shown that in the waking state the self appears, through ignorance, as connected with attachment, death (work), and the body and organs; in the dream state it is perceived as connected with desire, but free from the forms of death; and in the state of profound sleep it is perfectly serene and unattached, this nonattachment being the additional feature. If we consider all these passages together, the resulting sense is “that the self is by nature eternal, free, enlightened and pure. This comprehensive view has not yet been shown; hence the next paragraph. It will be stated later on that the self becomes such only in the state of profound sleep: ‘That is his form—beyond desires, free from evils, and fearless’ (IV. iii. 21). As it is such, i.e. unique, the self desires to enter this state. How is that? The next paragraph will explain it. As the meaning becomes clear through an illustration, one is being put forward.