Nanda undertook religious training for the sake of being born in heaven, where he would possess the beautiful women, because, relying on the law of cause and effect, he did not understand the wider Law of Causation. The people around him despised him because he sought only his own egoistic ends and ignored concord and the total development and perfection of others. After serious reflection, however, Nanda came to understand the Law of Causation.

Such understanding prompts awareness of the need to strive for the perfection of one’s own personality and of all society. If society as a whole improves and develops, the happiness of the individual will be guaranteed. If society is happy, the individual and all of his fellows will be happy. This is the meaning of true happiness and of the realization of the ideal Buddhist realm. Buddhist training is for the sake of realizing such a realm. When Nanda came to see this, he began training on the basis of the Law of Causation. This enabled him to attain the enlightenment of an arhat. (Page 96)

(See also How Nanda, Shakyamuni’s Half-Brother, Came To Be A Disciple)