The first is Brahmacharya-shrama or the stage of study. He uses the intellect and he learns about life through both study and practice. This is an intellectual attainment of knowledge.
From this he passes on to Gruhastha-shrama, the attainment of knowledge through practical experience of the responsibilities of life -- responsibility for wife, husband, children, home, the experience of living with neighbors, with enemies; doing one's duty by them in every way. All this is necessary before he can become a sage.
Next there is Wanaprashta-shrama, in which the aspirant goes beyond serving just his family. His consciousness comes to realize that all he has done for his family so far has been done for himself, for his wife and children. Now he must live for others, for the people of the town, of the country, of the race; he must even do what he can for the whole world. This is the service of humanity, the path of duty.
Finally he arrives at Sarmyasa-shrama, which is a life of retirement and solitude. This is the life of retreat. The man who has lived a life of honesty, virtue, goodness, and service is recognized as having done so by his wife and children, and they appreciate that now he should be allowed to follow the life of his own choice. They realize it is time for him to go into retreat. He must go into Sannyasa-shrama; but he does not do this unless his family consents.

Before describing this life I must explain why it is necessary. Why should not one always be in the world? Why the need for retirement at the latter part of life? This retirement is only too necessary. In the first place the man has given up all his life, all his time, all his energy, to the study of worldly things; secondly he has done all this in the interest of his family or perhaps for many people around him. It is right that he should some day have a rest. We ourselves feel justified in resting when Saturday comes, so why should he not have his Sunday after working all his life a life that has been nothing but continual conflict every moment, proving him to be wise and kind and gentle, true, honest, and virtuous through it all? His patience and virtue have been tested through all the temptations to which he was exposed, through all of life's difficulties, dangers, humiliations, and responsibilities that had to be faced. This man is surely justified, on reaching the fourth stage of life, in having a little peace, with no more worries or responsibilities of business or profession or even of his family. The world should leave him alone to think and meditate and let his muscles, bones, body, and mind be at rest. All this is natural.

So you cannot imagine anyone in the East, and especially in India, not longing from the time he was born for the day when he can become a sage. Whatever may have been his occupation, profession, business, trade, or family, he will have been longing for that moment when he could become a Vairagi at last, when he could cast off the load of responsibility that he had carried on his back all those years. He has longed for the time when he can give himself over to thinking about truth, having now peace and rest and opportunity to communicate with the eternal Being. He has all the time been hoping for his desire to be granted when he may have a rest, with enough time to think of God and live that life wherein one becomes capable of being one with God.