If every action gives raise to a subsequent series of effects, then how to escape its uninterrupted chain? That is, if karman's cycle is inescapable, there is no room for nirvāṇa (as the end of this-worldly transmigration, saṃsāra). Nor there is, indeed, for proper action. In fact, determinism implies the impossibility for one to perform a fully good action. As expressed in the Bhagavadgītā: action is surrounded by error, just like fire by smoke.
This could lead to either ethical nihilism (since there is no possible way to be good, let us behave in just whatever a way) or to non-action.
By the time the BhG was composed (around the beginning of the CE), the Hindū world had to seriously face this issue because of the presence of the Ajīvikas (the fatalist sect hinted at above), the Jainas and, most of all, because of the raise of Buddhism. This upheld a strict enchainment of cause and effects, but enhanced the ethical dimension of karman in spite of its ritual aspect.
Thus, the Hindū world is confronted with the idea that its account of karman leads to either ethical nihilism or to ascetism, which was at that time represented by antagonistic schools.
The Bhagavadgītā proposes a way-out of the dilemma: one is only responsible for one's desires, not for the action. Hence, although no freedom is possible in the precinct of action, there is still some space left for human initiative. One can decide to
- implement an action because one craves its results (and be consequently bound in the circle of saṃsāra, without any hope to get out of it
- follow the path of non-action (which is wrong, since it is determined by the selfish desire to avoid the results of one's deeds)
- implement an action without craving for its results
The idea is that a niṣkāma-karman (an action devoid of desire) bears no ethical consequence.
But how could one perform an action, if not out of desire? In fact, at the time of the BhG the other philosophical schools had already shown how an action is always initiated by one's desires.
The only way to supersede desire is to obey. I cannot initiate an action if I do not want it, unless I obey to someone else's order. Of course, the person I am obeying to must be ethically good. Else, my desire to obey to her would be itself liable to be blamed. In short, the BhG proposes as a ethical model obeyance to God. An action which is performed as an act of obeyance is ethically pure, since it does not bear the ethical consequence of one's craving for its results.
How can one, in every day life perform every action as an act of obeyance? Conforming to one's status, that is, to one's caste and state of age, as part of the order willed by God on the world.