(Sanskrit: Doctrine That All Is Real), important early Buddhist school of philosophy. A fundamental concept in Buddhist metaphysics is the assumption of the existence of dharmas, cosmic factors and events that combine momentarily under the influence of a person's past deeds to form a person's life flux, which he considers his personality and career. Differences arose among the various early Buddhist schools concerning the ontological reality of these dharmas. While, like all Buddhists, the Sarvāstivādins are idealists and consider everything empirical an illusion, they maintain that the dharma factors are eternally existing realities. The dharmas are thought to function momentarily, producing the empirical phenomena of the world, which is illusory, but to exist outside the empirical world. In contrast, the Sautrāntikas (those for whom the sūtras are authoritative) maintained that the dharma factors are not eternal but momentary, and the only actually existing dharmas are the ones presently functioning.

The Sarvāstivāda school is also known as the Vaibhāṣika because of the c. 2nd-century AD commentary Mahāvibhāṣa (“Great Elucidation”). This text was commented upon by the important 4th- or 5th-century Buddhist thinker Vasubandhu in his commentary Abhidharmakośa, prior to his conversion to the Mahāyāna tradition of Buddhism. Thus, elements of the Sarvāstivāda school came to influence Mahāyāna thought.