Swami Vivekananda said that the four castes, by turn, governed human society. The brahmin dominated the thought-current of the world during the glorious days of the ancient Hindu civilization. Then came the rule of the kshattriya, the military as manifested through the supremacy of Europe from the time of the Roman Empire to the middle of the seventeenth century. Next followed the rule of the vaisya, marked by the rise of America. The Swami prophesied the coming supremacy of the sudra class. After the completion of the cycle, he said, the spiritual culture would again assert itself and influence human civilization through the power of the brahmin. Swami Vivekananda often spoke of the future greatness of India as surpassing all her glories of the past.
Swami Nikhilananda, Swami Vivekânanda : A Biography (1975); the "vaisya" represent those primarily living at the mercantile levels of human motivation, and the sudra represent the working class, or laborers.