After laying down the foundation of the five causes (the initiating factor [kartā], the striving factor [ceṣṭā], the constraining factors [adhiṣṭhānaṁ, karaṇaṁ], and the ultimate sanctioning factor [daivaṁ]) of the results in action (in the previous section), Krishna explains in great detail how the quality of action can get adulterated with the modes of nature in various phases of manifestation of the action.

One whose (yasya) internal state (bhāvo) is not (na) governed by false ego (ahaṅkṛto), whose (yasya) power of discernment (buddhir) is not (na) tainted (lipyate), even while killing (hatvāpi) these people (sa imāḻ lokān), does not kill (na hanti) and is not bound (na nibadhyate) [by action]. (BG 18.17)

Knowledge (jñānaṁ), the object of knowledge (jñeyaṁ), and the knower (parijñātā) are the three types (tri-vidhā) of impetuses of action (karma-codanā). The senses (karaṇaṁ), the action (karma), and the performer (karteti) are the three (tri-vidhaḥ) constituents of action (karma-saṅgrahaḥ). (BG 18.18) Knowledge (jñānaṁ), the action (karma ca), and the performer of action (kartā ca) are at three levels (tridhaiva) distinguished based on the modes of material nature (guṇa-bhedataḥ). Let’s hear (chṛṇu) them as well (tāny api) in their true form (yathāvac). (BG 18.19)

Every action begins with the performer’s carrying a conception [material or spiritual] about himself or herself, the objects of this material world as well as the goal of life. Knowledge (jñānaṁ) here refers to one’s inner conceptions that encapsulate the basis of action. The defining characteristic of a performer is his or her motivation behind the action. So, we can associate the performer (kartā) with the performer’s motivation behind the action.

The performer’s conceptions, the motivation behind an action, and the action itself can get colored by the modes of nature. Before performing an action (karma), the conception (jñānaṁ), and motivation (kartā) of the performer come into play. During the performance of the action, the performer’s discernment (buddhi) to chalk out the details of the action at hand and inner conviction (dhṛti) to stay put in the action are driving the show. Overall, what matters before, during, and after the performance of the action is the experience of happiness (sukha) that the performer goes through in the process of executing the action. We can express these succinctly as follows:

Conception (jñānaṁ) + Motivation (kartā) + Action (karma) + Discernment (buddhi) + Conviction (dhṛti) => Experience (sukha)

So, Krishna henceforth discusses the qualitative influence of the modes of nature on each of these factors of action in great detail.