What is Guṇa in the Bhagavad Gita?
A guṇa is a strand or a thread. The Gita's claim is that everything made of nature, including your moods and your choices, is woven from three of them in changing proportion.
Sattva is clarity: light, settled, able to see. Rajas is drive: movement, restlessness, wanting. Tamas is heaviness: inertia, dullness, the refusal to move. Chapter 14 introduces them and chapters 17 and 18 apply the distinction to faith, food, sacrifice, discipline, giving, knowledge, action, the doer, understanding, steadiness and happiness, which is most of what a life consists of.
Two things are easy to get wrong. The first is to treat these as personality types. 18.40 says there is no being anywhere free of all three, which means they describe weather rather than character: you can be clear in the morning and heavy by four. The second is to assume clarity is the goal. 14.6 says sattva binds too, by attachment to pleasure and to knowing, and the grip of being somebody who understands is the subtlest binding in the book.
The verses 24
2.45
The scriptures deal with the three strands of nature.
3.27
Everything that gets done is done by the forces nature is made of.
7.12
Whatever states there are - clear, driven or heavy - know that they all come from me.
7.13
The whole world is fooled by these three states and does not recognise me, who am beyond them and do not wear out.
7.14
This divine play of mine, made of the three states, is very hard to get past.
13.21
Nature is said to be the cause in the matter of doing - of what is done and the means of doing it.
14.5
Clarity, drive and heaviness - these three strands, born of nature, bind the one who lives in a body, though that one does not perish.
14.6
Of these, clarity is pure and lights things up, and it is free of trouble.
14.7
Know that drive is passionate in nature, born of thirst and attachment.
14.8
Know that heaviness is born of not knowing, and it confuses everyone who lives in a body.
14.9
Clarity attaches you to being happy, Arjuna, and drive attaches you to action.
14.10
Clarity rises, Arjuna, by overcoming drive and heaviness.
14.11
When light appears at every gate of this body - when there is knowing - then you should understand that clarity has grown strong.
14.12
Greed, activity, the taking up of undertakings, restlessness, craving - these appear, best of the Bharatas, when drive has grown strong.
14.17
From clarity, knowing arises.
14.18
Those settled in clarity go upward.
14.20
Going beyond these three strands, which come with the body, one who has a body is freed from birth, from age, and from pain - and comes to what does not die.
14.22
Krishna said: Light, activity and confusion - he does not hate them when they come, Arjuna, and does not long for them when they go.
14.23
Sitting as though apart, not shaken by the strands - knowing that it is the strands that are at work, and standing firm, not wavering…
14.24
The same in pain and in pleasure, resting in himself; the same toward a clod of earth, a stone, and gold; the same toward what is liked and disliked; steady; the same under blame and praise…
14.25
… the same in honour and dishonour, the same toward the side of a friend and the side of an enemy, having given up every undertaking: that person is said to have gone beyond the strands.
17.2
Faith in people comes in three kinds, and it grows out of what a person already is.
18.19
Knowledge, action and the doer are each of three kinds, divided by the strands of nature.
18.40
There is no being anywhere, on earth or among the bright powers in the sky, that is free of these three strands born of nature.