Mandukya Karika, verse 4.67


उभे ह्यन्योन्यदृश्ये ते किं तदस्तीति नोच्यते ।
लक्षणाशून्यमुभयं तन्मतेनैव गृह्यते ॥ ६७ ॥

ubhe hyanyonyadṛśye te kiṃ tadastīti nocyate |
lakṣaṇāśūnyamubhayaṃ tanmatenaiva gṛhyate || 67 ||

67. Both (the mind and the Jīva) are objects of perception to each other. Which then can be said to exist independent of the other? (The reply of the wise is in the negative). Both are devoid of the marks by which they could be distinguished. For, either can be cognized only through the other.

Shankara Bhashya (commentary)

Both the mind and the Jīvas,1 or in other words, the mind and its modifications (which are seen as external objects) are each an object of perception to the other. In other words, one is perceived only through the other. The mind exists only in relation to the Jīva, etc., and the Jīva and objects exist only in relation to the mind. Therefore they are each an object of perception to the other. Hence2 wise men assert that nothing whatsoever, neither the mind nor its object, can be said to have any existence (if either be considered by itself)—(from the standpoint of either the idealist or the realist). As in the dream the elephant as well as the mind that perceives the elephant, are not really existent, so also is the case with the mind and its objects of the waking condition. How is it so? For, both the mind and its objects have no proof of their existence (independent of each other). They are each an object of perception to the other. One cannot cognize a jar without the cognition of a jar; nor can one have a cognition of a jar without a jar. In the case of the jar and the cognition of the jar it is not possible to conceive the distinction between the instrument of knowledge and the object of knowledge.