One of the great strengths of the Bhagavad Gita is its ability to act as a creative synthesis of a number of different streams of philosophy, religion and practical living, providing a new, comprehensive approach that values each one but places it within a larger context and framework within which it obtains new meaning. Two of these paths, Sankhya and Yoga are the subject of this new chapter. Sankhya, which provides an analytical framework for our understanding of the world we live in and its meaning, undergoes some modifications in order to assume its role in the Gita’s practical philosophy. Similarly, the Yoga espoused by the Bhagavad Gita also represents a somewhat different approach to the more traditional forms, such as Patanjali’s Raja Yoga or what we today in the West know as yoga, namely Hatha Yoga. In both cases, central aspects of each system are adopted and adapted to become part of the wider unifying action the Gita envisions.
Sri Aurobindo clarifies the Gita’s direction: “It is in fact primarily a practical system of Yoga that it teaches and it brings in metaphysical ideas only as explanatory of its practical system; nor does it merely declare Vedantic knowledge, but it founds knowledge and devotion upon works, even as it uplifts works to knowledge, their culmination, and informs them with devotion as their very heart and kernel of their spirit. Again its yoga is founded upon the analytical philosophy of the Sankhyas, takes that as a starting-point and always keeps it as a large element of its method and doctrine; but still it proceeds far beyond it, negatives even some of its characteristic tendencies and finds a means of reconciling the lower analytical knowledge of Sankhya with the higher synthetic and Vedantic truth.”
Sri Aurobindo, Essays on the Gita, First Series, Chapter 8, Sankhya and Yoga, pp. 62-63,