Meaning : A man who is in his youth cannot be regarded as merely a child. He is something else than a mere child. But at the same time he cannot be considered as altogether different from a child for if he is so, how can he be ashamed of the indiscretions of his childhood ? In the same manner if the young man is entirely different from the old man which he is likely to be in future, we can not account for endeavour in securing qualities for his future. He, therefore, must be considered as identical with the old man in future.
Thus the man appears to be one and the same on account of the abiding characteristics of caste, family, form, qualities, name and others while the same man appears to be changing or perishing on account of his different states such as childhood, youth and old age. Moreover on account of his sense of shame his past mistakes and preference for the qualities in future, the man must be considered as one and the same person in all states and at all times.
Exactly similar is the case with the soul. Like the man in the above illustration, it must be considered as one, as well as many, the same as well as different - when we look at it with reference to bondage and liberation and happiness and misery etc.