Bhagavad Gita does not profess to have proclaimed any new doctrine. Krishna has declared in shlokas 4.1 to 4.3 that the spiritual wisdom which was being revealed to Arjuna was the imperishable science of yoga which was passed down, in the ancient times, from sage to sage. With passage of time, this knowledge was lost to the world. The teachings of Gita were a renewal of this long forgotten truth. Though it does not say anything which was not said before, still it gives a clearer vision of the basic truths and opens up new channels for understanding the secrets of life. It has bestowed mankind with a science and an art by which he can gain worldly glory and also spiritual bliss. It, in fact, represents the perpetual communion between God and the man.
The different schools of Hindu thought, which were competing with each other at the time of composition of Gita, have been brought together and merged seamlessly into an organic unity. It has refined and reconciled various beliefs and practices of that period and transformed them into different aspects of a wholesome way of temporal and spiritual life. Apparently conflicting currents of philosophical and religious thought were fused together to provide the mankind with a cosmic as well as a moral order which was of universal validity, relevant for all time and all men. Gita has demonstrated as to how can the varied streams of thought converge towards the same goal.
Bhagavad Gita has presented the truth in its various shades. It has woven wisdom, work and worship in one thread. It has been declared that all these paths of liberation namely gyana yoga, karma yoga and bhakti yoga are not contradictory to each other. They are, in fact, complementary to one another. One can attain perfection by sincerely following the path chosen by him.
Relationship of the individual soul to the Supersoul has differently been interpreted by dvaita (dualism), advaita (non-dualism) and vishishtadvaita (qualified non-dualism) schools of Hindu philosophy. Without specifically mentioning these metaphysical concepts, Gita has lent credence to all these streams of thought. Further, it has been proclaimed that purusha (the conscious nature) and prakriti (the material nature) are the two natures of the Supreme. God is both, the conscious and material cause of the world. The fact that the changeless reality and the transitory world arise from the same source implies that the soul and the body are not alien to each other. Whereas the soul permeates the life of the body, the bodily life also leaves its impact on the soul. The man represents vital unity of body and the soul.
As per Gita, there is no chasm between unmanifest Brahman, the Absolute, and the manifest Ishvara, the Supreme Lord. They are not two different truths. The highest reality is Brahman. It is self-existent. It is undifferentiated pure consciousness. But when the same reality is perceived from the point of view of creation, He is Ishvara, the Personal God. Ishvara is responsible for the creation, preservation and dissolution of the entire cosmos. As it is difficult for an ordinary human being to relate to the unmanifest, therefore, common people prefer to worship God in one or the other manifested form.
In Gita, Krishana is the manifested God. He is the Supreme Lord. He also represents the ultimate reality, the Unmanifest Eternal. Those who worship Him with faith and devotion, attain His eternal abode. And the prayers of those who worship other gods are also answered by the grace of the Supreme Lord. Name and form of various gods is used to reach the formless Divine. Thus, there is oneness of the Supreme and His various forms.
The importance of scriptures on the path of spiritual evolution has time and again been highlighted by Krishna. But ritual observances are of little value for the one who has attained freedom of the spirit. It has been stated that for the one who has understood the Absolute, Vedas have the same importance as a pond in a place flooded with water all around.
Bhagavad Gita has described various kinds of spiritual practices. All these acts of devotion such as performance of various yagyas, meditation, mantra chants and breath control are means to spiritual growth. But it has been emphasised that practices for gaining knowledge are superior to the practices for gaining material things because it is wisdom which leads to liberation of the soul.
There is no antithesis between eternity and the continuity of time. The past, present and the future derive their existence from the eternity. Unity between the eternal and a period of time has been established in Gita through the personality of Krishna. He is beyond the concepts of time and space. Yet he is a historical figure also. The Supreme Lord is both, the eternal and also the incarnation living at a particular time.
To conclude, Bhagavad Gita has not only brought different streams of thought under one umbrella, but has also suggested practical ways of achieving the ultimate goal. It addresses various human problems and explores myriad possibilities till man is able to obtain ever lasting peace and experience spontaneous joy.