Chapter Three begins with Arjuna expressing a misunderstanding of what Krishna explained in Chapter Two.
Arjuna said, “If you say intelligence is better than work [karma], why are you trying to get me involved in these terrible deeds? I’m confused by this contradiction, so please tell me plainly, what is better for me: action or intelligence?”
All-Attractive Krishna replied: “Arjuna, I already explained that yogis synthesize two paths: the scientific path of philosophy [jñāna-yoga] and the practical path of action [karma-yoga].” 
The path proposed by Krishna in Bhagavad-Gītā is a synthesis philosophy and practice. ‘Put intelligence into practice,” Krishna previously said.
Arjuna might ask, “Why must they be synthesized? Why not just cultivate philosophy?”
“You cannot get free from worldliness just by sitting around doing nothing. Renunciation itself is not the goal.” 
Arjuna would ask, “Why not?”
“No one can ever pass a single moment without doing something. Everyone is helplessly forced to act, habituated by their very nature.” 
The very nature of spirit itself is dynamic and active. Therefore perfect inactivity is literally impossible.
“But what about the ‘sadhus’ sitting in the forest doing nothing but meditating?” Arjuna would ask.
“They keep their senses repressed, but their minds reminisce on sense objects. That’s why they are known as ‘pretenders.’ They are in self-denial.” 
Pretenders make a show of giving up worldly possessions and activities, when their minds are still full of selfish desires. Thus when they sit in their caves in perfect postures their minds very often reminisce on food, sex and infinitely various mundane knick-knacks.
“Sense-control begins from the mind, Arjuna. The best path is to use the senses intelligently, without lust.” 
Effective spiritualists begin their efforts with the mind. Pretenders begin with external changes, because such things are visible and demonstrable to the public – whose admiration and applause they covertly covet. Sincere spiritualists focus first on transforming their inner selves – knowing that the outer self will automatically and naturally follow suit. Therefore the best path forward in spiritual evolution is to cultivate intelligence, while keeping the senses engaged in a positive, productive and dutiful manner.
“Do your duties responsibly. That is certainly better than giving them up. You cannot even keep your body functioning if you give up action.” 
Arjuna will protest, “But sensual action is supposed to be the cause of bondage!?” So Krishna explains:
“Work only for the sake of ‘sacrifice.’ If you work for your own worldly desires you will suffer degradation and bondage; but if you work as a sacrifice you will become perfectly liberated.” 
Krishna points out the difference between spiritually progressive and materially degrading action. Working for selfish aims is ‘sense-gratification’ and leads to degradation. Working for the sake of sacrifice is purifying.
Arjuna will ask, “But even if I work as a sacrifice, results will come to me, and I will enjoy them. For example, if I fight out of duty and win, I will enjoy a kingdom. Will accepting the kingdom implicate me in sense gratification?”
Krishna will explain that the results of sacrificial action are wholesome and keep the body fit and happy.
“The Creator created duties along with civilization and said, ‘May these duties make you prosperous and fulfill your every desire!  Please the gods by these duties, and they will be pleased with you. This win-win scenario will enable your ultimate welfare!  Pleased by your dutiful sacrifices, the gods will bless you with everything you desire. Don’t be a thief and try to enjoy without sacrifice and duty.  Those who eat the food that remains after their duties are complete is relieved from all sufferings; but those who try to enjoy food they prepare only for themselves incur grievous bondage.  Never treat anything as being separate from the divine: Your bodies are made from the nutrients in food. Food comes from rain. Rain comes from sacrifice, and sacrifice is the natural result of being dutiful.  Duties are defined by the Vedas, which are created by spiritual sound waves. Therefore spirituality permeates responsible duty. ‘”
Krishna gave an elaborate quote on behalf of Brahmā, the Creator, which accurately represents the ancient Vedic concept of intertwined social morality and spirituality. The essence of the statement is that those who responsibly fulfill their duties can rightfully enjoy the healthy byproducts of their good deeds. ‘Sensual’ action, connoting degradation, is to attempt to enjoy the world without being dutiful and responsible.
 There is a double-entendre here because in Sanskrit ‘Sacrifice’ [Yajña] is widely used as a proper name for Viṣṇu, the Supreme Personality of Godhead. The double meaning is that the best sacrifice is one done for the sake of Viṣṇu, Godhead.