While the essential methodologies and principles of Sankhya and Yoga are maintained in the Gita, it does not accept all of the specific details or conclusions of either path as narrowly defined by either a strict philosophical system in the case of the Sankhya, or a strict inner psychological discipline as found in Patanjali. The Gita also finds a way to reconcile the two paths, apparently so different on the surface.
Sri Aurobindo explains: “Its Sankhya is the catholic and Vedantic Sankhya such as we find it in its first principles and elements in the great Vedantic synthesis of the Upanishads and in the later developments of the Puranas. Its idea of Yoga is that large idea of a principally subjective practice and inner change, necessary for the finding of the Self or the union with God, of which the Rajayoga is only one special application. The Gita insists that Sankhya and Yoga are not two different, incompatible and discordant systems, but one in their principle and aim; they differ only in their method and starting-point. The Sankhya is also a Yoga, but it proceeds by knowledge; it starts, that is to say, by intellectual discrimination and analysis of the principles of our being and attains its aim through the vision and possession of the Truth. Yoga, on the other hand, proceeds by works; it is in its first principle Karmayoga; but it is evident from the whole teaching of the Gita and its later definitions that the word karma is used in a very wide sense and that by Yoga is meant the selfless devotion of all the inner as well as the outer activities as a sacrifice to the Lord of all works, offered to the Eternal as Master of all the soul’s energies and austerities. Yoga is the practice of the Truth of which knowledge gives the vision, and its practice has for its motor-power a spirit of illumined devotion, of calm or fervent consecration to that which knowledge sees to be the Highest.”
Sri Aurobindo, Essays on the Gita, First Series, Chapter 8, Sankhya and Yoga, pp. 63-64,