The key to unlocking the solution to the issue raised by the Gita regarding determinism versus free will has been provided by Sri Aurobindo, who points out that there is an ascending scale of manifested consciousness. The more “involved” the consciousness is, the fewer characteristics of free will it is able to manifest; while the more consciousness has evolved, the more we see signs of the development of a free will. This in turn corresponds to the predominance of one or another of the Gunas of Nature at each stage.
Sri Aurobindo provides an analysis, starting with the level that predominates in Tamas. “How the passage from subjection to mastery works out is best seen if we observe the working of the Gunas in the scale of Nature from the bottom to the top. At the bottom are the existences in which the principle of Tamas is supreme, the beings who have not yet attained to the light of self-consciousness and are utterly driven by the current of Nature. There is a will even in the atom, but we see clearly enough that it is not free will, because it is mechanical and the atom does not possess the will, but is possessed by it.” “Tamas, the inert and ignorant principle, has its grip on it, contains rajas, conceals sattva within itself and holds a high holiday of mastery, Nature compelling this form of existence to act with a stupendous force indeed, but as a mechanical instrument….”
With the development of plant life, the quality of tamas remains primary, but we begin to see an increasing action of rajas and the initial responsiveness of sattva entering slowly into the picture. Once we move beyond the evolution of plants, we see tamas receding as first rajas, then sattva play a larger role, and as this occurs, we see the exercise of a more independent action than the purely mechanical action of the plane of Matter dominated by tamas.
Sri Aurobindo, Essays on the Gita, First Series, Chapter 21, The Determinism of Nature, pp. 208-209