Without ignorance (about objects), which is dense like darkness, knowledge (about objects) does not exist; similarly without knowledge (about objects), that ignorance does not exist. Only the knowledge which knows the non-existence of the individual self (the ego) who is the base (of knowledge and ignorance about objects), (by enquiring ‘To whom are that knowledge and ignorance?’) is (true) Knowledge.
Sri Ramana Maharshi - Ulladu Narpadu-Reality In Forty Verses, V.10
Note: Knowledge about objects, and ignorance about objects are a dyad or dvandva, each of which depends upon the other for its seeming existence. If there did not previously exist an ignorance of a thing, the knowledge of that thing could not come into existence. And only when the knowledge of that thing dawns, do we come to know that an ignorance of it existed previously. Thus without our present knowledge of that thing, our prior ignorance would not be known and hence would not exist.
Since knowledge and ignorance about objects are both mere thoughts, they can rise only after the rising of the first thought, the ego. But when one enquires ‘who am I’, the individual to whom both knowledge and ignorance arise?’, one will realize that the ego or individual who experiences knowledge and ignorance about objects is truly non-existent, and that Self alone truly exists. Only that Knowledge which thus knows the non-existence of the ego and the sole existence of Self, is true Knowledge. That knowledge is Self.
http://www.happinessofbeing.com/Sri_Ramanopadesa_Noonmalai.pdf
