The 9th and 8th centuries BCE witnessed the composition of the earliest Upanishads. Upanishads form the theoretical basis of classical Hinduism and are known as Vedanta (conclusion of the Veda). The older Upanishads launched attacks of increasing intensity on the rituals, however, a philosophical and allegorical meaning is also given to these rituals. In some later Upanishads there is a spirit of accommodation towards rituals. The tendency which appears in the philosophical hymns of the Vedas to reduce the number of gods to one principle becomes prominent in the Upanishads. The diverse monistic speculations of the Upanishads were synthesised into a theistic framework by the sacred Hindu scripture "Bhagavad Gita".