It is customary for historians of the philosophy and religion of India to commence their studies with the Rig-Veda, which is regarded as the earliest sacred text of ancient Indian culture. A study of the Vedas forms generally the beginning of an advanced learning in the philosophical and religious literature of India. The Rig-Veda is a book of metrical hymns and is divided into ten parts called Mandalas. Another division of the book is into eight sections called Ashtakas. The hymns of the Rig-Veda, called mantras, are powerfully constructed poems, with an amazing power of rhythm, spontaneity and sublimity of effect, and charged with soulful inspiration, usually with four feet of the metre into which every poem is cast. The poem is pregnant with great meaning and force which can be directed, by a proper recitation of it, for or against any objective here or hereafter. The hymn has the power to protect (trayate) the one who contemplates (mananat) on it, and hence the name mantra. The mantras of the Vedas are intended to invoke the deities to whom they are addressed, and to summon the power of the deities for executing an ideal. They are the means of connection with the denizens of the celestial world and the divinities that immanently guard and perform different functions in the various planes of existence. There are also mantras addressed in glorification of the Universal Being or the Absolute.  

The Vedas are classified into four groups, called Rik, Yajus, Saman and Atharva. The Rig-Veda is primarily concerned with panegyrics to the gods in the heavens, and is the main book of mantras. The Yajur Veda is classified into the Krishna (black) and Sukla (white) recensions. The Yajur Veda contains mainly sacrificial formulae in prose and verse to be chanted at the performance of a sacrifice. The Sama Veda consists mostly of verses from the Rig-Veda set to music for singing during the sacrifice. The Atharva Veda abounds mainly in spells and incantations in verse meant for different lower purposes than the purely spiritual.  

Every Veda has four divisions, called the Samhita, Brahmana, Aranyaka and Upanishad. The Samhita portion of the Vedas embodies the hymns or prayers offered to deities, as already mentioned. The Brahmanas are the ritualistic portion of the Vedas which expatiate on the details of performing sacrifices. The most famous and costly of these sacrifices are the Rajasuya, Asvamedha, Agnishtoma and Soma Yaga, undertaken either for earthly sovereignty or for heavenly joy. There are many minor sacrifices for the performance of which directions are given in the Brahmanas. The mantras of the Samhitas are supposed to be recited in the sacrifices, mainly. They can, however, also be used as pure spiritual exercises in prayer and meditation, which aspect received emphasis in a development that led to the philosophic mysticism of the Upanishads, as we shall see later.

The Veda Mantras are, as stated above, praises offered to the deities, or Devas, who are regarded as capable of bestowing any blessing on man. It does not mean, however, that the poets of the Samhitas were ignorant of the existence of the Supreme Being and that the gods of the Vedas are mere puerile personifications of the processes of Nature, as many Western orientalists are inclined to think. The Veda Mantras are not the ignorant prattle of immature cattle grazers, the pastoral hymns of primitive minds, as certain historians opine. The historical evaluation should not be oblivious of the logical grounding of process, whether of thought or of society. The trend of visualising the manifold as expressions of the One, and the One as revealing itself in the many is unmistakably traceable in the hymns of the Rig-Veda. It is true that the main gods of the Vedas are Indra, Varuna, Agni, Surya (Aditya or Savitr), Soma, Yama, Vayu, Asvins, Brihaspati and Brahmanaspati; and a correct chanting of the mantras, summoning the power of the divinities could produce supernatural results, and even the actual materialisation of them here. But it is easy to discover at the same time, in the Rig-Veda, the germinal sources of the concepts of Vishnu, Rudra and Prajapati or Hiranyagarbha as universal divine presences and as the supreme gods of the cosmos. We must reserve for treatment another grander concept - the Supreme Being enunciated in the Purusha Sukta and the Nasadiya Sukta.  

In the Purusha Sukta or the hymn of the Cosmic Person, we have the most magnificent description of the spiritual unity of the cosmos. Here is given, perhaps, the earliest complete presentation of the nature of Reality as both immanent and transcendent. The all-encompassing Purusha, who is all-heads, all-eyes and all-limbs, everywhere, envelops and permeates creation from all sides and stands above it as the glorious immortal. The Purusha is all that was, is and shall be. The whole universe is a small fraction of Him, as it were, for He ranges above it in His infinitude of glory. Such is the majestic Purusha, the God of all gods. From Him proceeds the original creative Will (later identified with Brahma, Hiranyagarbha or Prajapati), by which this vast universe was projected in space and time. The Purusha Sukta proclaims once and for all, the organic inseparability of the constituents of society. The Vedic seer loved mankind and creation as much as he loved God.  

The Nasadiya Sukta of the Rig-Veda gives, for the first time, intimations of the seer's sounding the depths of being. The astounding vision of the transcendent by the relative is the apparent theme of this famous hymn. Though the Absolute is the Being above all being, existence beyond all possible concepts about it, it becomes an intriguing something, about which nothing definite can be said and of which no definition can be given, when it is envisaged by the individual. Reality is here depicted as not capable of being designated either as existence or non-existence, for there was none to perceive it then, before the manifestation of the heaven and the earth. There was, as if, only an indescribable stillness, deep in its content and defying all approach to it by anyone. There was neither death nor immortality, for there was no differentiatedness whatsoever. Naturally, there was neither day nor night. There was only That One Presence, throbbing in all splendour and glory but appearing as darkness to the eye that would like to behold it. There was nothing second to it; it alone was. From it this creation arose. But how it all happened no one can say, for everyone came after creation. This is the central point of the Nasadiya hymn, a development of which leads to the various ramifications of philosophic and religious thought in the Upanishads and the later classical established form of religion. In a famous mantra, the Rig-Veda declares that 'Existence (or Reality) is one, though, the wise ones call it by various epithets like Indra, Mitra, Varuna, Agni, Yama, Vayu', thus unifying all the gods in a single Being.  

There are other Suktas in the Rig-Veda, which are of great importance in different ways. The Asyavamasya Sukta has a very complicated structure of meaning and hints at certain vital issues of the creation and pattern of the universe. The Hiranyagarbha Sukta sings of the rise of the universe from the cosmic Hiranyagarbha or Prajapati (who is later identified with Brahma, the Creator). The Aghamarshana Sukta refers to the cycle of creation from the cosmic equilibrium in the beginning, in a recurring manner, so that the essential features of creation repeat themselves in every cycle. The Vamadeva Sukta mentions the spiritual realisation of sage Vamadeva even while he was in the womb of his mother and his exclamations of joy on his attainment of freedom from the fetters that bound him to individuality. The concluding portion of the Rig-Veda is a heartening call to unity in thought, word and deed among people, a message which has so much meaning to humanity today.  

The Rudra Adhyaya or the Satarudriya, a hymn of the Yajur Veda, is a thrilling invocation of the Supreme Being as Rudra-Siva, wherein He is addressed in all the visible and conceivable forms. The Almighty Lord is the big and small, the gross and subtle, the low and high, the distant and near, the visible and invisible, what is and what is not. This is an address of invocation to Siva as the all-comprehensive being, ready to shower blessings on the devotees who crave for His grace. The Purusha Sukta and the Rudra Adhyaya are chanted even this day during worship in the temples of India, as invocatory and purificatory process for bringing about world-solidarity and commonweal. The Vedic Almighty God combines in Himself aesthetic beauty and splendour, ethical goodness and law, and spiritual reality and perfection, all in one.  

The Gayatri Mantra stands unparalleled in the Vedas, and it is regarded as their seed-word, which, with the three Vyahritis (Bhuh, Bhuvah, Svah), according to Manu, is supposed to have been the 'open-sesame' for universal manifestation at the commencement of time.  

The Rig-Veda gives two code words: satya and rita, signifying the spiritual law as such and the law in its working process in the cosmos. While satya is the principle of integration rooted in the Absolute, rita is its application and function as the rule and order operating in the universe. Sometimes rita is interpreted as the original principle of being and satya its manifestation. The world is sustained by a just and inexorable law which is the decree of God for the well-being of all. Conformity with this law tends to material and spiritual progress and advancement, leading to higher forms of integration in life, while its violation is punished with a series of transmigratory lives in the different planes of manifestation.  

In the Purusha Sukta we observe the concept of sacrifice carried to the degree of perfection where the whole universe is regarded as an act of sacrifice on the part of God. God becomes in the form of creation the field and opportunity for individual sacrifice. The universe is a sacrifice (yajna), and all actions, properly performed, in so far as they involve an element of self-abnegation for self-transcendence, are forms of sacrifice of one's individuality or whatever belongs to it as its appendage. The Supreme Being Himself is a transcendent sacrifice when viewed in the form of this manifestation, when the relative is construed as a self-alienation of the Divine Being. The essence of sacrifice is existence for others' sake, not necessarily in the form of social activity, but in a wider perspective of consciousness which gets engulfed gradually in a series of its higher reaches, pointing to a final absoluteness of being. This is the concept of supreme sacrifice in the Purusha Sukta.  

From the point of view of such lofty thoughts as embodied in the Purusha Sukta and the Rudra Adhyaya, the adoration and contemplation of God is possible in any place and at any time, for God is here, just before us, and He can be worshipped through anything in the universe. In this worship and contemplation, which is the highest sacrifice, God is the articles of worship, He is the worship, the worshipper and also the worshipped. His existence and manifestation mean one and the same thing. His being and activity constitute a single whole. Immortality and death, life and non-life are both His modes. The Supreme Being is here and now. He can be realised by this mighty act of universal self-sacrifice.  

To the seers of the Vedas, life is a joy of sacrifice, and a daily visualisation of Divinity in all Nature.

The principles of rita and satya imply a strict adherence to law and rule in conformity with the aim and purpose of the processes of the universe. Any action which originates in a sense of personal individuality set in opposition to or incongruous with the universal order of rita and satya should obviously mean the work of a nemesis, as a natural reaction to such action, endeavouring to set right the balance of cosmic equilibrium which has been disturbed by it. This principle of the redounding of the effect of action upon the doer of it is the metaphysical, ethical and psychological regulative force called karma, which requires the doer of such action to pass through a series of experiential processes called metempsychosis or rebirth in other conditions and environments than that in which the action has been done. Thus it would be clear that the law of karma and reincarnation is a scientific law of the integrality of the cosmos. The Vedas accept the operation of this principle and recognise the fact that one's future life depends on the way one lives the present one. We shall have occasion to revert to this famous doctrine of karma and samsara in our studies of its further development.

The Vedas may be regarded as the source and fountain to which the later developments of thought can be traced. The bold speculative trend and philosophic flights of the Vedas culminated in the Upanishads and the system of the Vedanta. Their descriptions of religious ecstasy in divine contemplations inspired the formulation of the school of Yoga which was codified in the aphorisms of Patanjali. Their visions of the creation of the universe helped the rise of the Sankhya doctrine which regularised the prevalent notions on cosmology and psychology. The logical trend in the Vedas stimulated the development of anvikshiki (application of reason) and the rationalistic bias of certain systems among the darsanas. The ritualistic and sacerdotal emphasis in the Vedas laid the foundation for the purely authoritarian Mimamsa school. The forms of meditation and prayer predominant in the Vedic hymns sponsored the building up of the Bhakti schools among the Vaishnavas, Saivas and Saktas. The accounts of sages, anchorites and kings which the Vedas furnish, formed the beginnings of the elaborate Itihasas or epics, and the Puranas. The social rules and customs of the time of the Vedas became the cornerstones for the systematisation of conduct and law in the Smritis or Dharmasastras. The social, political and religious institutions were all meant to help the gradual evolution of the individual, according to each one's capacity and aptitude, towards the realisation of spiritual universality.