The Sushruta Samhita and Caraka Samhita have religious ideas throughout, states Steven Engler, who then concludes "Vedic elements are too central to be discounted as marginal". These ideas include treating the cow as sacred, extensive use of terms and same metaphors that are pervasive in the Hindu scriptures – the Vedas, and the inclusion of theory of Karma, self (Atman) and Brahman (metaphysical reality) along the lines of those found in ancient Hindu texts. However, adds Engler, the text also includes another layer of ideas, where empirical rational ideas flourish in competition or cooperation with religious ideas.