Bhagavad Gita Verse 30, Chapter 18

pravrittim cha nivrittim cha kaaryaakaarye bhayaabhaye |
bandham moksham cha yaa vetti buddhihi saa paartha saattvikee || 30 ||
 
That intellect which knows engagement and withdrawal, what is duty and what is not, fear and fearlessness, bondage and liberation, O Paartha, that is saattvic.
 
pravrittim : engagement
cha : and
nivrittim : withdrawal
cha : and
kaaryaakaarye : what is duty and what is not
bhayaabhaye : fear and fearlessness
bandham : bondage
moksham : liberation
cha : and
yaa : which
vetti : knows
buddhihi : intellect
saa : that
paartha : O Paartha
saattvikee : is saattvic
 
Our jnyaanam, our knowledge, gives us an object to pursue, person to approach, or situation to create. Now it is upto our buddhi, our intellect, to decide the course of action. Typically, for any objectve, we need to decide whether or not we want pursue the objective, and if we do, how should we go about doing it. Shri Krishna says that a saattvic intellect, a saattvic buddhi is one that is clear on those two factors. In fact, Shri Krishna breaks the two factors down into four assessments: assessing one's stage in life and one's svadharma first, then whether an action is one's duty or not, then whether to be fearful or not, and lastly, whether to continue to act or not.
 
As we will see in a later topic in this chapter, the varna aashrama system, the system of aptitude and stage of life, helps us determine whether we should act at all, and if so, which actions should we perform and which we should not. A student should focus on studying, not in creating a family. A soldier should focus on protecting his country, not making money by selling his country out. The varna aashrama system helps address the first two assessments: engagement and withdrawal, and what is our duty and what is not. For example, if we get a new business proposal, we should assess whether we have the aptitude to execute it, but also, whether we are in the right stage of life. It is no use starting a new business when we are in our late sixties.
 
Once the varna aashrama system has approved the performance of an action, we need to test whether the action is motivated by personal reward, or whether it is motivated by selfless service. If we have fear in our mind while performing an action, chances are that a trace of egoism has crept into it. We may be doing the action out of the need for praise and honour. But if our mind is fearless, we can assume that our action is motivated out of selflessness. Lastly, as we perform one action after another, we should always examine whether these actions are taking us closer to liberation, or are further entrenching us in the material world. An intellect that guides us in such a manner is termed saattvic.

Bhagavad Gita Verse 34, Chapter 13

kshetrakshetrajnyayorevamantaram jnyaanachakshushaa |
bhootaprakritimoksham cha ye viduryanti te param || 34 ||
 
Those who, by the eye of wisdom, perceive the distinction between the field and its knower in this manner, and relinquishment from the cause of all beings, they attain the supreme.
 
kshetrakshetrajnyayoho : field and its knower
evam : in this manner
antaram : distinction
jnyaanachakshushaa : eye of wisdom
bhootaprakriti : cause of all beings
moksham : relinquishment
cha : and
ye : those who
viduhu : perceive
yanti : attain
te : they
param : supreme
 
After having understood the true nature of the self, the nature of the ignorance we are in, and also having understood the method of how to remove this ignorance, what is the result? Shri Krishna concludes this chapter by asserting that the one who has removed his ignorance through knowledge attain the supreme, which is moksha or liberation from the cycle of Prakriti’s creation and dissolution. The key to understanding this chapter is "viveka", or discrimination, which was hinted at the beginning of this chapter by the words "idam shareera" or "this body".
 
Take the case of a forensic investigator who is hired to detect counterfeit currency notes. On the first day of his job, he will not be able to spot the difference between a fake note and a genuine note. After learning about the visual differences between what’s fake and what’s genuine, and after practising to spot those differences over a period of time, his eye will begin to see minute details that the average eye cannot see. This ability to separate the real from the unreal is discrimination, which is the “eye of wisdom” mentioned in the shloka.
 
So then, the one who knows how to conduct his life in a manner such that he can distinguish between the unreal aspects and the real aspects, between the field and its knower, between Purusha and Prakriti, and learn to see the imperishable in the perishable as Ishvara, such a person is freed of the mechanisms of Prakriti, the cause of all beings. This is the goal of jnyaana yoga, which is summarized in the thirteenth chapter of the Gita. We will be able to attain this goal if we bring this teaching into our lives through constant reflection and meditation.
 
om tatsatiti shreematbhagavatgitasupanishadsu brahmavidyaayaam yogashaastre shreekrishnaarjunsamvade kshetrakshetrajnyavibhaagayogo naama trayodashodhyaayaha || 13 ||