The Vedic literature refers to a minor atmospheric deity, with fearsome powers called Rudra. The Rigveda, for example, has 3 out of 1,028 hymns dedicated to Rudra, and he finds occasional mention in other hymns of the same text. The term Shiva also appears in the Rigveda, but simply as an epithet, that means "kind, auspicious", one of the adjectives used to describe many different Vedic deities. While fierce ruthless natural phenomenon and storm-related Rudra is feared in the hymns of the Rigveda, the beneficial rains he brings are welcomed as Shiva aspect of him. This healing, nurturing, life-enabling aspect emerges in the Vedas as Rudra-Shiva, and in post-Vedic literature ultimately as Shiva who combines the destructive and constructive powers, the terrific and the gentle, as the ultimate recycler and rejuvenator of all existence.
The similarities between the iconography and theologies of Shiva with Greek and European deities have led to proposals for an Indo-European link for Shiva, or lateral exchanges with ancient central Asian cultures. His contrasting aspects such as being terrifying or blissful depending on the situation, are similar to those of the Greek god Dionysus, as are their iconic associations with bull, snakes, anger, bravery, dancing and carefree life. The ancient Greek texts of the time of Alexander the Great call Shiva as "Indian Dionysus", or alternatively call Dionysus as ""god of the Orient"". Similarly, the use of phallic symbol as an icon for Shiva is also found for Irish, Nordic, Greek (Dionysus) and Roman deities, as was the idea of this aniconic column linking heaven and earth among early Indo-Aryans, states Roger Woodward. Others contest such proposals, and suggest Shiva to have emerged from indigenous pre-Aryan tribal origins.
Three-headed Shiva, Gandhara, 2nd century AD
Shiva as we know him today shares many features with the Vedic god Rudra, and both Shiva and Rudra are viewed as the same personality in Hindu scriptures. The two names are used synonymously. Rudra, the god of the roaring storm, is usually portrayed in accordance with the element he represents as a fierce, destructive deity.
The oldest surviving text of Hinduism is the Rig Veda, which is dated to between 1700 and 1100 BC based on linguistic and philological evidence. A god named Rudra is mentioned in the Rig Veda. The name Rudra is still used as a name for Shiva. In RV 2.33, he is described as the "Father of the Rudras", a group of storm gods.
The hymn 10.92 of the Rigveda states that deity Rudra has two natures, one wild and cruel (Rudra), another that is kind and tranquil (Shiva). The Vedic texts do not mention bull or any animal as the transport vehicle ("vahana") of Rudra or other deities. However, post-Vedic texts such as the Mahabharata and the Puranas state the Nandi bull, the Indian zebu, in particular, as the vehicle of Rudra and of Shiva, thereby unmistakably linking them as same.
Rudra and Agni have a close relationship. The identification between Agni and Rudra in the Vedic literature was an important factor in the process of Rudra's gradual development into the later character as Rudra-Shiva. The identification of Agni with Rudra is explicitly noted in the "Nirukta", an important early text on etymology, which says, "Agni is also called Rudra." The interconnections between the two deities are complex, and according to Stella Kramrisch:The fire myth of "Rudra-Śiva" plays on the whole gamut of fire, valuing all its potentialities and phases, from conflagration to illumination.In the "Śatarudrīya", some epithets of Rudra, such as "Sasipañjara" ("Of golden red hue as of flame") and "Tivaṣīmati" ("Flaming bright"), suggest a fusing of the two deities. Agni is said to be a bull, and Lord Shiva possesses a bull as his vehicle, Nandi. The horns of Agni, who is sometimes characterized as a bull, are mentioned. In medieval sculpture, both Agni and the form of Shiva known as Bhairava have flaming hair as a special feature.
Vima Kadphises with ithyphallic Shiva.
Coin of the Kushan Empire (1st-century BCE to 2nd-century CE). The right image has been interpreted as Shiva with trident and bull.
According to Wendy Doniger, the Puranic Shiva is a continuation of the Vedic Indra. Doniger gives several reasons for her hypothesis. Both are associated with mountains, rivers, male fertility, fierceness, fearlessness, warfare, the transgression of established mores, the Aum sound, the Supreme Self. In the Rig Veda the term 'śiva' is used to refer to Indra. (2.20.3, 6.45.17, and 8.93.3.) Indra, like Shiva, is likened to a bull. In the Rig Veda, Rudra is the father of the Maruts, but he is never associated with their warlike exploits as is Indra.
The Vedic beliefs and practices of the pre-classical era were closely related to the hypothesised Proto-Indo-European religion, and the pre-Islamic Indo-Iranian religion. The earliest iconic artworks of Shiva may be from Gandhara and northwest parts of ancient India. There is some uncertainty as the artwork that has survived is damaged and they show some overlap with meditative Buddha-related artwork, but the presence of Shiva's trident and phallic symbolism in this art suggests it was likely Shiva. Numismatics research suggests that numerous coins of the ancient Kushan Empire that have survived, were images of a god who is probably Shiva. The Shiva in Kushan coins is referred to as Oesho of unclear etymology and origins, but the simultaneous presence of Indra and Shiva in the Kushan era artwork suggest that they were revered deities by the start of the Kushan Empire.
The texts and artwork of Jainism show Indra as a dancer, although not identical generally resembling the dancing Shiva artwork found in Hinduism, particularly in their respective mudras. For example, in the Jain caves at Ellora, extensive carvings show dancing Indra next to the images of Tirthankaras in a manner similar to Shiva Nataraja. The similarities in the dance iconography suggests that there may be a link between ancient Indra and Shiva.
Rudra's evolution from a minor Vedic deity to a supreme being is first evidenced in the "Shvetashvatara Upanishad" (400–200 BC), according to Gavin Flood. Prior to it, the Upanishadic literature is monistic, and the "Shvetashvatara" text presents the earliest seeds of theistic devotion to Rudra-Shiva. Here Rudra-Shiva is identified as the creator of the cosmos and liberator of souls from the birth-rebirth cycle. The period of 200 BC to 100 AD also marks the beginning of the Shaiva tradition focused on the worship of Shiva as evidenced in other literature of this period. Shaiva devotees and ascetics are mentioned in Patanjali's "Mahābhāṣya" (2nd-century BC) and in the "Mahabharata". Other scholars such as Robert Hume and Doris Srinivasan state that the "Shvetashvatara Upanishad" presents pluralism, pantheism, or henotheism, rather than being a text just on Shiva theism.
Self-realization and Shaiva Upanishads
He who sees himself in all beings,
And all beings in him,
attains the highest Brahman,
not by any other means.
The Shaiva Upanishads are a group of 14 minor Upanishads of Hinduism variously dated from the last centuries of the 1st millennium BCE through the 17th century. These extol Shiva as the metaphysical unchanging reality Brahman and the Atman (soul, self), and include sections about rites and symbolisms related to Shiva.