The concept of ‘avatāra’ (incarnation of the Divine) is one of the fundamental tenets of Hinduism. The locus classicus of the theory of avatāra is in the Bhagavad-gītā (4.5-8).
After creating this world, God sets it in motion and regulates it through the cosmic law known as ṛta, satya or dharma. When the cosmic law, the ṛta, is comprehended by the intellect, it becomes ‘satya’ (truth). When life is regulated according to it, it becomes ‘dharma’ (righteousness, right conduct).
Since the human mind is a product of the three guṇas (sattva, rajas and tamas), it is subject to vicissitudes. In the beginning sattva will have the upper hand and people will naturally be inclined towards dharma. Hence life on earth moves smoothly in harmony and peace. Gradually, as rajas and tamas gain ascend-ance, people will incline towards evil; and this will upset the social equilibrium. Good people devoted to dharma will be neutralised and made ineffective whereas the evil ones addicted to adharma or unrighteousness will rule the roost. At such critical periods in human history God decides to ‘come down’ (avatāra = coming down) in a human form (or even in a non-human form if that is necessary) and restore the spiritual and social equilibrium implied by the word ‘dharma.’
Though restoring dharma is the primary concern of an avatāra, eliminating or chastising the wicked, and, protecting the good—being a necessary and integral part of this process—are also undertaken by him.
An avatāra is not just a jīva who has attained the state of liberation and is eager to help mankind. He represents the direct descent of God himself to the human level in order to help the human beings to ascend to the divine level, of which the liberated soul is a perfect example. A jīva is forced to take a body due to his past actions (prārabdha-karma) whereas the avatāra incarnates of his own free will for saving mankind. Consequently, he is always conscious of his mission and power. It is only he who can see both the Absolute (Brahman) and the manifested world simultaneously and can teach the world about the Absolute.
Vedānta admits of God’s manifestation as the world, his omniscience as also omnipotence and grace. Hence there is nothing unreasonable in the doctrine that he can also assume a special and unique form as avatāra, fully retaining consciousness of the divinity from his very birth.
Another speciality of this doctrine is that God incarnates himself in response to the needs of the times wherever and whenever necessary. Hence there are no restrictions regarding either the number of incarnations or the place. The sole consideration is the decline of dharma and the rise of adharma in opposition to it, to such an extent that the social equi-librium is badly disturbed.
The avatāra concept is probably suggested in the Ṛgveda itself (3.53.8; 6.47.18) where Indra is said to be endowed with the mysterious power of assuming any form at will. Some of the avatāras mentioned in the lists of the ‘Daśāvatāras’ (ten incarnations) are met with in the earlier Vedic literature. The Śatapatha Brāhmaṇa mentions the story of Matsya (fish incarnation) as also of the Kūrma (tortoise incarnation) and of the Varāha (boar incarnation) (vide 184.108.40.206-6; 220.127.116.11; 18.104.22.168). The Vāmanāvatāra (dwarf incarnation) of Viṣṇu taking the three steps is also clearly mentioned in the same scriptures (22.214.171.124).
Coming to the age of the epics and the purāṇas we find a tendency towards limiting the avatāras to ten (hence the name ‘Daśāvatāras’ or ten incarnations) the last one (Kalki) being yet to come. The Daśāvatāras are: Matsya (the fish), Kūrma (the tortoise), Varāha (the boar), Narasiṁha (the man-lion), Vāmana (the dwarf), Paraśurāma (Rāma with the battle-axe), Rāma (the son of Daśaratha), Kṛṣṇa (the son of Vasudeva), Buddha (Gautama Buddha) and Kalki. However, there is no unanimity or uniformity in the various lists given by these works. Around the tenth century A. D., Buddha seems to have gained a place in the lists as the ninth incarnation. In the earlier lists as also the later ones, Buddha has been replaced by Balarāma (Rāma of strength, elder brother of Kṛṣṇa). Some lists include both Balarāma and Buddha but omit Kṛṣṇa, the raison d’etre being that all the ten are the avatāras of Kṛṣṇa who is the Lord Viṣṇu Himself.
Sometimes we come across many more avatāras than the traditional ten. For instance, the Bhāgavata gives three lists of 22 names (1.3.6-22), 23 names (2.7.1 ff.) and 16 names (11.4.3 ff.) and also declares that the avatāras are innumerable (1.3.26).
Occasionally the avatāras are classified into three types: pūrṇāvatāra, aṁśāvatāra and āveśāvatāra. Pūrṇāva-tāras are those in which the manifestation of the Divine is full and complete (pūrṇa = full) as in Rāma and Kṛṣṇa. Aṁśāva-tāras are partial manifestations (aṁśa = part) of the Divine as in great sages like Vyāsa. Āveśāvatāras are those in which there is a temporary entry of the Divine (āveśa = entry) as in the case of Nṛsiṁha manifesting through Padmapāda (a disciple of Śaṅkara) who was a votary of that deity.