The ritualistic performances of sacrifice are meant for material economic development; in other words, they are meant to keep the body in good condition for cultivation of spiritual knowledge. But for actual attainment of spiritual knowledge, other qualifications are needed. What is essential is vidya, or worship of the Supreme Lord. Sometimes the word yoga is used to refer to the gymnastic performances of different bodily postures which help mental concentration. Generally, the different bodily postures in the yoga system are accepted by less intelligent men to be the end of yoga, but actually they are meant to concentrate the mind upon the Supersoul. After creating persons for economic development, Brahma created sages who would set the example for spiritual realization.