The Bhagavat Geetha literally "The song of the Lord", occurs in the Bheeshma parva section of the MahAbhAratha. The scene upon which the discourse is set, is a philosophically ideal one where man is forced to confront the ultimate questions of life.
The righteous Pandavas and their evil cousins the Kauravas, of the race of the Kuru, face each other in the battle field. Due to family loyalties and diplomatic obligations friends, dear relatives, revered elders and teachers of the Pandavas are forced to take the side of the Kauravas in the war. On the morning of the first day of the war before the battle can begin Arjuna the foremost Pandava warrior suddenly in a flash of remorse at the thought of fighting his near and dear ones throws down his weapons saying that he would rather be killed by them than fight against them. He argues that it is greed, which had blinded his cousins and it was for those with wisdom to understand the situation and to forgive and forget. To engage in violence would only lead to the destruction of the family and the values it had nourished and lived by, which in turn would lead to the ruin of the society itself.
Lord Krishna the divine incarnation (avataaram) of Lord Vishnu who is acting as Arjuna's charioteer in the war, chides him for being unmanly, faint hearted and for grieving over what should not be grieved. The wise do not worry about birth and death. Never had there been a time when he and Arjuna didn't exist and never will there be a time when they will cease to exist, for they were in truth not the body which is subject to death, but the indestructible Self or the Atman which is unborn and eternal. Krishna further instructs Arjuna on the dharma of a kshatriya - that it is the duty of a warrior and a righteous man to fight evil and restore peace and order. During the discourse Lord Krishna repeatedly asks Arjuna to fight and at the end simply says : "do as you please".
In the course of the dialogue Lord Krishna also lectures Arjuna on the true purpose of life i.e., liberation from the cycle of rebirths and the paths leading to it. The way of works (karma yoga) and way of devotion (bhakti yoga) placed alongside the traditional way of knowledge (jnaana yoga) as means to liberation, gives credence to the suggestion that the Geetha tries to combine popular religion with the idealism of the Upanishads.
The fundamental teaching of the Geetha is that the Real always is and the unreal never is. The limited and transient world - the object of experience - is not real. The senses, body and mind are also not real as they too are subject to change and decay. The Real is the Self or the Atman, the ultimate subject, which is our true self and the controller of the senses and the mind. It is akrtr or the non-doer, the mere witness to all the actions of praakriti, which constitutes the senses, the mind and the body. The Self is the indestructible essence in man - unborn, eternal, all pervasive, immovable, ancient and unmanifest. It is neither born nor does it die. In death it is only the body, which is destroyed and not the Self. When the body perishes the immortal and everlasting Self is said to take on a new body.In its metaphysical aspect the Self underlies and animates all phenomena. So he who sees this reality in all beings, himself in others and others in himself, the unchanging in all change, is said to be wise. Though some of the teachings in the Geetha seem to support the doctrine of the plurality of Selves, there is also an underlying absolutist implication which brings all the diversity of the world under one single Reality.
The goal of the Geetha is yoga i.e., union of the individual self with the infinite Self. Being beyond the senses and the intellect the Self can be reached in three ways - karma yoga or the way of works, bhakti yoga or the way of devotion and jnaana yoga or the way of knowledge. This division roughly maps to three common temperaments found in man - the willful, the emotional and the intellectual. But though the paths are distinguished thus, it is only at the preparatory stages and at the final stage all of them stand synthesized. The union of the individual with the absolute, the greatest of achievements, is the end of suffering, a state of equanimity and absolute bliss.
Jnaana yoga is the path of knowledge. In the Upanishads knowledge is the way, the means and the end i.e., knowledge of the transience and the unreality of the empirical world is the way to turn away from the things of sense; knowledge of the Self is the means to liberation; and the final goal - the Self itself is said to be knowledge. Likewise the Geetha also enjoins the primacy of knowledge and asserts that liberation cannot be attained without knowledge. Even the result of bhakti towards the Lord is that knowledge is granted by the Lord to effect liberation. Knowledge is the culmination of karma too. Whatever be the efforts towards control of the senses and desire, our lust for material life cannot be permanently overcome without knowledge. The Geetha gives such a high place to knowledge that it says even the most sinful man can be freed from bondage through jnaana alone. There's nothing purer than knowledge.
The Geetha does not advocate one to renounce action, but to practice renunciation in action. Non-action is impossible due to the three constituent gunas of praakriti - sattva, rajas and tamas - which necessarily gives rise to action. Action is that which moves the world and is an integral part of life. So instead of going against nature the Geetha approaches the problem through a different angle. Action itself can be used to help one's spiritual progress. Normal action, which implies an underlying desire binds man to samsAra. By performing works without desire, with a detached spirit, without expecting the fruits of the labor, one can escape the bonds of samsAra. The Geetha does not advocate the annihilation of all desires, but merging of all desires into one supreme desire of spiritual liberation. SamnyAsam is thus not renunciation of action, but renunciation of interest, desire and attachment while performing actions. But even this spirit of detachment during action can be achieved only through knowledge.
On the realization of the Self, when all individuality is obliterated, such detachment in action comes naturally. So the perfect yogi works for the good of humanity in a spirit of detachment and selflessness, with no desire to reap the fruits of action.
Bhakti or devotion too is a form of karma. It is disinterested service to God and can be practiced by anybody. But again as even such disinterested service requires knowledge, the higher levels of bhakti is possible only for a true jnAni. Those who practice bhakti are given assurance of the Lord's protection. Even a man of ill conduct can overcome his defects through bhakti and obtain lasting tranquility. "O Arjuna, know firmly that my devotee is never ruined. He who does my work, who yields himself to me, who is devoted to me, void of attachment, without hatred towards anyone, comes to me". One has to submit entirely to the mercy of the Lord with absolute faith. "Merge your mind in me, be my devotee, prostrate yourself before me and you shall come to me. I pledge you my word; you are dear to me. Abandoning all dharmas come to me alone for shelter; worry not, I'll liberate you from all sins".
The true bhakta sees the Lord in everything and everything in the Lord. He knows that the Lord pervades the entire universe (vasudevah sarvam) and the immanent inner controller of all. "When devotion is perfect, then the individual and his God become suffused into one spiritual ecstasy and reveal themselves as aspects of one life. Absolute monism is therefore the completion of the dualism with which the devotional consciousness begins".
Relation to other systems
The Geetha is heavily influenced by the Upanishads. The popular saying is that the Upanishads of cows, Krishna is the milker, Arjuna the calf and the nectar like Geetha is the excellent milk. The Geetha is not shruti or the Veda, which was only open to the males of the top three castes - the brahmin, the kshatriya and the vaishya. It is smriti or "that which was remembered", open to all orders and the women. Hence we see the dilution of the Upanishadic ideal of knowledge, that path which is so hard that the Katha Upanishad equates it to walking on the edge of a razor and suitable only for samnyAsins. Bhakti and karma seem to have been introduced to accommodate the spiritually uninitiated. But again the Geetha is clear that bhakti and karma too are but manifestations of knowledge and knowledge is the only way to liberation. In its theistic inclinations and Krishna worship the Geetha seems to have been influenced by the Bhaagavatha cult.
The use of the words "Saamkhya" and "Yoga" in the Geetha are not in connection with the philosophical systems bearing the names. As Shankaraachaarya clarifies, saamkhya means knowledge and yoga means practice. Though there're certain similarities between the Geetha and the two systems - Purusha, Praakriti, the theory of the gunas, that knowledge is the ultimate liberator - there're differences too. Praakriti in both Saamkhya and Yoga is an independent entity apart from the Purusha, while the Geetha considers it as the power (maya) of God. Also while the two schools assert the plurality of Purushas, the Geetha considers individual jivas as parts of the one reality - God is immanent in all creation. While Samkhya has no place for a creator God, the Geetha is openly theistic. While liberation for both Samkhya and Yoga is the separation of the Purusha from Praakriti, for the Geetha it is union of the individual self with the Supreme Self. Unlike the negative kaivalya of the Samkhya, the spiritual ideal of the Geetha is the Upanishadic sat-chit-Ananda - existence, knowledge and bliss.