The Yogācārabhūmi introduces and justifies five fields of science, pañcavidyāsthāna, which are learning the Buddha’s speech, grammar, medicine, logic, and the mundane arts and crafts. In the Bodhisattvabhūmi chapter, it is stated that Boddhisattvas, who aim not only to attain their own liberation but also to rescue suffering beings, should learn all five subjects. The examination of relevant texts demonstrates that this Bodhisattva idea reflects a change in the ideal type of Buddhist practitioner. An early Buddhist text, the Suttanipāta, regards ideal Buddhists as those who concentrate on their own spiritual cultivation and do not pay attention to learning medicine, ritual formulae, and the interpretation of signs, which are not directly related to Buddha’s teachings. In a later Mahāyāna text, however, knowledge beyond the Buddha’s own teachings was regarded as useful for helping other beings, which would in turn increase faith in Buddhism. Therefore, the establishment of five sciences can be regarded as a phenomenon corresponding to the emphasis on altruism, which is ultimately connected to proselytization, within the Buddhist tradition.