Two books and a quotation by a later philosopher make up nearly the whole record. A poem of about 900 verses, the Bodhicaryāvatāra, and a prose anthology, the Śikṣāsamuccaya, survive in Sanskrit under the name Śāntideva. Śāntarakṣita, a later Indian Buddhist philosopher, quoted him in a text composed by about 763, while Yijing, a Chinese pilgrim who left India in 685, does not mention him. Historians therefore place him between the late seventh and the middle of the eighth century.
He wrote for the Mahāyāna, the Great Vehicle, whose ideal is the bodhisattva: someone who sets out to become a Buddha for the sake of every other being. That ideal asks a person to weigh a stranger's suffering as heavily as their own. Śāntideva argued for it from an account of what exists; drawing ethics directly from metaphysics in this way is, according to the Internet Encyclopedia of Philosophy, unusual in South Asian Buddhism. The metaphysics was that of Madhyamaka, the Middle Way school founded by Nāgārjuna: nothing has a nature of its own, and the self least of all.
The claim he is remembered for stands in the eighth chapter of the poem. If fear and suffering are as unwelcome to others as they are to me, what is special about me, that I guard against my own and not against theirs? The ordinary answer is that my pain is mine. Śāntideva removes the owner. The continuum of a life and the collection of its parts, he argues, are unreal in the way a queue or an army is unreal, a single name for many things. Suffering therefore belongs to no one, and it is to be prevented simply because it is suffering. The sixth chapter turns the same reasoning on anger. A person who hurts you acts under causes they did not choose, like the bile that brings on great pain — and nobody is angry at bile.
The Śikṣāsamuccaya reaches the same ideal by another road. More than a hundred Mahāyāna sūtras speak in it, quoted as the word of the Buddha and arranged around twenty-seven short verses by Śāntideva himself, and some of those scriptures survive in Sanskrit only through his quotations. The poem tells its reader to study the anthology again and again for the detail of right conduct.
Everything else told about the man comes from the Tibetan historians Bu-ston and Tāranātha, writing centuries later. Their biographies make him a prince of Saurāṣṭra, in today's Gujarat, who became a monk at Nālandā, the great monastic university of northern India. His fellow monks, they say, nicknamed him Bhusuku. When the assembly asked him to recite, he delivered the poem, and partway through the ninth chapter he rose into the air and vanished while a voice finished the text. The tradition adds that the Śikṣāsamuccaya was found in his room beside a Sūtrasamuccaya, which cannot be identified with any surviving text.
By the early ninth century the poem had been translated into Tibetan. Tsongkhapa, founder of the Geluk school, quoted it at length, and the present Dalai Lama has called it the highest inspiration for his ideals. In the West, the scholar Luis Gómez judged it probably the third most translated text of Indian Buddhism. Philosophers set the queue argument beside Derek Parfit's Reasons and Persons of 1984; the scholar of Buddhism Paul Williams objected in Altruism and Reality in 1998 that suffering makes little sense without someone who suffers, and Mark Siderits defended Śāntideva against him in 2000. Charles Goodman, who translated the anthology in 2016, reads him as a consequentialist, an ethicist who judges acts by their results. Other scholars doubt that texts written as guides to practice hold an ethical theory at all, and the question is still argued.