'I think, I speak, I grasp, I hear,' so beginning with (these) forms
Action is done by the Supreme Self, which is the Self of the mind-stuff and senses.
Commentary
The Supreme Self is the witness of action performed by the totality of mind and senses. This totality is called the Self of the mind-stuff and senses. The Siva Purana says, "I am the seer and the doer." The Supreme Self appears to be doing action, but it is because of the nature of the mind and senses that action is done. Action ceases when the mind and senses are calmed down. Action is prompted by outer impressions and inner urges. When they totally cease and the mind is free and clear, the Self is realized. The Katha Upanishad (III. 3-4) has a fine description of this: "Know that the Self rides in a chariot, with the physical body as the chariot. Know that intuitive judgement is the chariot driver, and that the mind is the reins. They say the senses are the horses."
It is the Supreme Self which is the true basis of the totality of phenomenal existence,—"All this is the Absolute,"—whether collective or individual. The mind-stuff and senses are only reflective images of this totality. As the Svetasvatara Upanishad (I. 16) says, "The Self pervades all objects, like butter is contained in cream."
All action is grounded in the Self, because without the Self there is no existence. To be free one must go beyond the mind and senses to what is non-changing, non-conceptual and non-dual. That is the Self-Absolute. Attain the Self-Absolute and there will be no return.