I thought it was the three gunas sattwa, rajas and tamas being mentioned but I wasn’t sure how tamas could correlate to action-force at all. Perhaps these are something else.
Tamas is not mentioned because it is about activity that he is speaking. Tamas is inertia and sets in to balance the activity. The three forces are part of the tantra. They are powers that move us, the will in life, gyan shakti, iksha shakti, kriya shakti. The knowledge should be there, then the will to execute it and the power of action in the instruments to do what knowledge has seen as the thing to be done, the will has accepted and impels and the instrument that responds to the will. This is not the triple modes of Nature but the triple forces behind all activity.
Affectionately,
Alok Da
