Shruti or Shruthi (Sanskrit: श्रुति, IAST: Śruti, IPA: [ɕrʊtɪ]) in Sanskrit means "that which is heard" and refers to the body of most authoritative, ancient religious texts comprising the central canon of Hinduism. Manusmriti states that Śrutistu vedo vigneyah (Sanskrit: श्रुतिस्तु वेदो विज्ञेय:, lit. means "Know that Vedas are Śruti"). Thus, it includes the four Vedas including its four types of embedded texts—the Samhitas, the early Upanishads, the Brahmanas and the Aranyakas.
Śrutis have been variously described as a revelation through anubhava (direct experience), or of primordial origins realized by ancient Rishis. In Hindu tradition, they have been referred to as apauruṣeya (not created by humans). The Śruti texts themselves assert that they were skillfully created by Rishis (sages), after inspired creativity, just as a carpenter builds a chariot.
All six orthodox schools of Hinduism accept the authority of śruti,[note 1] but many scholars in these schools denied that the śrutis are divine. Nāstika (heterodox) philosophies such as the Cārvākas did not accept the authority of the śrutis and considered them to be flawed human works. A popular quote on supreme authority is Śruti can be found in Manusmriti (Adhyaya 1, Mantra 132) that Dharma jijñāsamānam pramāṇam paramam śrutih (Sanskrit: धर्मं जिज्ञासमानानां प्रमाणं परमं श्रुतिः, lit. means "To those who seek the knowledge of the sacred law the supreme authority is the revelation (Śruti )").
Shruti (Śruti) differs from other sources of Hindu philosophy, particularly smṛti "which is remembered" or textual material. These works span much of the history of Hinduism, beginning with the earliest known texts and ending in the early historical period with the later Upanishads. Of the śrutis, the Upanishads alone are widely known, and the central ideas of the Upanishadic śrutis are at the spiritual core of Hindus.
The Sanskrit word "श्रुति" (IAST: Śruti, IPA: [ɕɽʊt̪ɪ]) has multiple meanings depending on context. It means "hearing, listening", a call to "listen to a speech", any form of communication that is aggregate of sounds (news, report, rumour, noise, hearsay). The word is also found in ancient geometry texts of India, where it means "the diagonal of a tetragon or hypotenuse of a triangle", and is a synonym of karna. The word śruti is also found in ancient Indian music literature, where it means "a particular division of the octave, a quarter tone or interval" out of twenty-two enumerated major tones, minor tones, and semitones. In music, it refers the smallest measure of sound a human being can detect, and the set of twenty-two śruti and forty four half Shruti, stretching from about 250 Hz to 500 Hz, is called the Shruti octave.
In scholarly works on Hinduism, śruti refers to ancient Vedic texts from India. Monier-Williams traces the contextual history of this meaning of śruti as, "which has been heard or communicated from the beginning, sacred knowledge that was only heard and verbally transmitted from generation to generation, the Veda, from earliest Rishis (sages) in Vedic tradition. In scholarly literature, Śruti is also spelled as Shruti.
Smriti literally "that which is remembered," refers to a body of Hindu texts usually attributed to an author, traditionally written down but constantly revised, in contrast to Śrutis (the Vedic literature) considered authorless, that were transmitted verbally across the generations and fixed. Smriti is a derivative secondary work and is considered less authoritative than Sruti in Hinduism. Sruti are fixed and its originals preserved better, while each Smriti text exists in many versions, with many different readings. Smritis were considered fluid and freely rewritten by anyone in ancient and medieval Hindu tradition.
Both śrutis and smṛtis represent categories of texts of different traditions of Hindu philosophy. According to Gokul Narang, the Sruti are asserted to be of divine origin in the mythologies of the Puranas. In contrast, states Roy Perrett, ancient and medieval Hindu philosophers have denied that śruti are divine, authored by God.
The Mīmāṃsā tradition, famous in Hindu tradition for its Sruti exegetical contributions, radically critiqued the notion and any relevance for concepts such as "author", the "sacred text" or divine origins of Sruti; the Mimamsa school claimed that the relevant question is the meaning of the Sruti, values appropriate for human beings in it, and the commitment to it.
Nāstika philosophical schools such as the Cārvākas of the first millennium BCE did not accept the authority of the śrutis and considered them to be human works suffering from incoherent rhapsodies, inconsistencies and tautologies.
Each of these Vedas include the following texts, and these belong to the śruti canon:
Of the above śrutis, the Upanishads are most widely known, and the central ideas of them are the spiritual foundation of Hinduism. Patrick Olivelle writes,
Even though theoretically the whole of Vedic corpus is accepted as revealed truth [śruti], in reality it is the Upanishads that have continued to influence the life and thought of the various religious traditions that we have come to call Hindu. Upanishads are the scriptures par excellence of Hinduism.
वेदोऽखिलो धर्ममूलं स्मृतिशीले च तद्विदाम् ।
आचारश्चैव साधूनामात्मनस्तुष्टिरेव च ॥
Translation 1: The whole Veda is the (first) source of the sacred law, next the tradition and the virtuous conduct of those who know the (Veda further), also the customs of holy men, and (finally) self-satisfaction (Atmanastushti).
Translation 2: The root of the religion is the entire Veda, and (then) the tradition and customs of those who know (the Veda), and the conduct of virtuous people, and what is satisfactory to oneself.
वेदः स्मृतिः सदाचारः स्वस्य च प्रियमात्मनः ।
एतच्चतुर्विधं प्राहुः साक्षाद् धर्मस्य लक्षणम् ॥
Translation 1: The Veda, the sacred tradition, the customs of virtuous men, and one's own pleasure, they declare to be the fourfold means of defining the sacred law.
Translation 2: The Veda, tradition, the conduct of good people, and what is pleasing to oneself – they say that is four fold mark of religion.
Only three of the four types of texts in the Vedas have behavioral precepts:
For the Hindu all belief takes its source and its justification in the Vedas [Śruti]. Consequently every rule of dharma must find its foundation in the Veda. Strictly speaking, the Samhitas do not even include a single precept which could be used directly as a rule of conduct. One can find there only references to usage which falls within the scope of dharma. By contrast, the Brahmanas, the Aranyakas and the Upanishads contain numerous precepts which propound rules governing behavior.
Bilimoria states the role of śruti in Hinduism has been inspired by "the belief in a higher natural cosmic order (Rta succeeded later by the concept Dharma) that regulates the universe and provides the basis for its growth, flourishing and sustenance – be that of the gods, human beings, animals and eco-formations".
Levinson states that the role of śruti and smṛti in Hindu law is as a source of guidance, and its tradition cultivates the principle that "the facts and circumstances of any particular case determine what is good or bad". The later Hindu texts include fourfold sources of dharma, states Levinson, which include atmanastushti (satisfaction of one's conscience), sadacara (local norms of virtuous individuals), smṛti and śruti.
The śrutis, the oldest of which trace back to the second millennium BCE, had not been committed to writing in ancient times. These were developed and transmitted verbally, from one generation to the next, for nearly two millenniums. Almost all printed editions available in the modern era are copied manuscripts that are hardly older than 500 years. Michael Witzel explains this oral tradition as follows:
The Vedic texts were orally composed and transmitted, without the use of script, in an unbroken line of transmission from teacher to student that was formalized early on. This ensured an impeccable textual transmission superior to the classical texts of other cultures; it is, in fact, something like a tape-recording.... Not just the actual words, but even the long-lost musical (tonal) accent (as in old Greek or in Japanese) has been preserved up to the present.
Ancient Indians developed techniques for listening, memorization and recitation of śrutis. Many forms of recitation or pathas were designed to aid accuracy in recitation and the transmission of the Vedas and other knowledge texts from one generation to the next. All hymns in each Veda were recited in this way; for example, all 1,028 hymns with 10,600 verses of the Rigveda was preserved in this way; as were all other Vedas including the Principal Upanishads, as well as the Vedangas. Each text was recited in a number of ways, to ensure that the different methods of recitation acted as a cross check on the other. Pierre-Sylvain Filliozat summarizes this as follows:
These extraordinary retention techniques guaranteed an accurate Śruti, fixed across the generations, not just in terms of unaltered word order but also in terms of sound. That these methods have been effective, is testified to by the preservation of the most ancient Indian religious text, the Ṛgveda (ca. 1500 BCE).
This part of a Vedic student's education was called svādhyāya. The systematic method of learning, memorization and practice, enabled these texts to be transmitted from generation to generation with inordinate fidelity.
Swami Sivananda in his book Self-Knowledge stated: "The Srutis are authoritative. They will guide you. They will inspire and elevate you. You must have unshakable faith in their teachings. Then only you will be saved from the clutches of Maya or death. Do not destroy them by means of your sophisticated reasoning. The intellect is a frail and finite instrument. Do not depend upon your intellect alone. If you do so, there is no hope for attaining immortality."