Try to understand the structure of the mind; the mind contains the whole universe. All individual experiences of thoughts, feeling, perception, mental formation are happenings within the mind, which appears and disappears as waking or dream. A continuous process of thought, a continuous procession of thoughts -- associated, non-associated, relevant, and irrelevant -- many multi-dimensional impressions gathered from everywhere are belongs to the individual who perceives the world within the mind. The birth, life, death and the world exit within the mind their reality is limited to mind. The nature of the mind is impermanence because it is bound by form, time and space.
A child is born. A child is clear because the ego is not formed. The moment ego appears, the unclarity, the confusion, enters. A child is clear, clarity but he will have to gather knowledge, information, culture, religion, and conditionings necessary, useful to the worldly life. He will have to gather many things from everywhere, from many sources -- opposite, contradictory sources. From many sources he will gather. Then the he becomes store house of hotchpotch knowledge. And because of so many diverse knowledge, doubts and confusion is bound to be there. And whatsoever he gather, nothing is certain, because knowledge based on the ego is always a growing affair. Therefore, there is need to acquire Self-Knowledge to get rid of accumulated dross.