Caste in its original conception was not a hereditary status, but a classification based on man's natural capacities. In his evolution, man passes through four distinct grades, designated by ancient Hindu sages as Sudra, Vaisya, Kshatriya, and Brahmin.
The Sudra is interested primarily in satisfying his bodily needs and desires; the work that best suits his state of development is bodily labor.
The Vaisya is ambitious for worldly gain as well as for satisfaction of the senses; he has more creative ability than the Sudra and seeks occupation as a farmer, a businessman, an artist, or wherever his mental energy finds fulfillment.
The Kshatriya, having through many lives fulfilled the desires of the Sudra and Vaisya states, begins to seek the meaning of life; he tries to overcome his bad habits, to control his senses, and to do what is right. Kshatriyas by occupation are noble rulers, statesmen, warriors.
The Brahmin has overcome his lower nature, has a natural affinity for spiritual pursuits, and is God-knowing, able therefore to teach and help liberate others.