This chapter is often considered the summary of the entire Bhagavad Gita. It contains 72 verses. After asking Krishna for help, Arjuna is instructed into various subjects such as, Karma yoga, Jnana yoga, Sankhya yoga, Buddhi yoga and the immortal nature of the soul. Sankhya here refers to one of six orthodox schools of the Hindu Philosophy.

Sankhya yoga is a philosophy established by sage Kapila. Essence of Sankhya yoga is removal of suffering by cultivating discrimination and by releasing the soul (purusha) from its entanglement in matter (prakriti). The word samkhya means “number or analysis”. Samkhya also means perfect knowledge. Samkhya represents the theory and Yoga represents the application or the practice.

Purusha is the Transcendental Self. It is absolute, independent, free, imperceptible, unknowable, above any experience and beyond any words or explanation.

Prakriti is the material cause of the world. Prakriti is dynamic. Its dynamism is attributed to its constituent gunas. Prakriti is the non-self. It is devoid of consciousness Prakriti is unintelligible and gets greatly influenced by the Purusha, the self. It can only manifest itself as the various objects of experience of the Purusha. Prakriti is constituted of three gunas, namely sattva, rajas and tamas.

Krishna explains the immortal nature of the soul and encourages Arjuna to not see the results of action, but rather focus on the work itself.

Lord Krishna said:

You are mourning for those
not worthy of sorrow; yet speaking
like one knowledgeable. The wise person
neither laments for the the dead or the living. (11)

Truly there never was a time
When I was not, nor you, nor these
kings of men–nor in the future
A time when we shall cease to be. (12)

Just as a soul dwelling in a body goes through
childhood, youth, and old age, 
so it leaves one body and enters another.
The wise one does not grieve about
this. (13)

Truly material contacts
Produce cold, heat, pleasure, and pain.
Impermanent, they come and go,
Learn to endure them, Bharata. (14)

He whom these things do not afflict,
The same in pain or in pleasure,
That wise one, O Leader of Men,
Is fit for immortality. (15)

The unreal never comes to be,
The real does never cease to be.
The certainty of both of these
Is known to those who see the truth. (16)

That by Which all is pervaded–
Know That is indestructible.
There is none with the power to
Destroy the Imperishable. (17)

These bodies inhabited by
The eternal embodied Self
Are declared to come to an end.
Therefore now fight, O Bharata. (18)

He who thinks the Self is slayer
And he who thinks the Self is slain–
Neither of the two understands;
The Self slays not, nor is it slain. (19)

The soul never takes birth, and never dies at any time
Nor does it come into being again when the body is created.
The soul is birthless, eternal, perpetual, primeval,
It is never destroyed when the body is destroyed. (20)

In what way can he who knows this–
Indestructible, eternal,
Birthless and imperishable–
Slay or cause another to slay? (21)

Even as a man casts off his worn-out clothes
And then clothes himself in others which are new
So the embodied casts off worn-out bodies
And then enters into others which are new. (22)

This self by weapons is cut not;
This self by fire is burnt not;
This self by water is wet not;
And this self is by wind dried not. (23)

This self cannot be cut, nor burnt,
Nor wetted, nor dried: It is changeless,
All-pervading and unmoving,
Immovable, eternal self. (24)

Unmanifest, unthinkable,
This Self is called unchangeable.
Therefore, knowing this to be such,
You surely ought never to mourn. (25)

And if you think this self to have
Constant birth and death–even then,
O mighty-armed, you should not be
Impelled for this reason to grieve. (26)

Of that which is born, death is sure,
Of that which is dead, birth is sure.
Over the unavoidable,
Therefore you never should lament. (27)

All beings are unmanifest
In their beginning, Bharata,
Manifest in their middle state,
Unmanifest then in their end.(28)

Someone perceives this self as being wondrous,
Another speaks of it as being wondrous,
Another hears of it as being wondrous,
And another, hearing, does not understand. (29)

This indweller in all bodies
Is ever indestructible.
Therefore you should not, Bharata,
Ever mourn for any creature. (30)

And looking at your own dharma,
You surely ought never waver,
For there is nothing better than
A righteous war for Kshatriyas. (31)

Fortunate are those Kshatriyas,
Who thus are called, O Arjuna,
To fight in a battle like this,
That comes to them as heaven’s gate. (32)

But if you refuse to engage
In righteous warfare, Arjuna,
Then forfeiting your own dharma
And honor you shall incur sin. (33)

The world will also ever hold
You as a craven reprobate.
To the honored such disrepute
Is surely worse even than death. (34)

The great car-warriors will believe
You shrink back from battle through fear.
And you will be lightly esteemed
By those who have thought much of you. (35)

Your enemies, then cavilling
At your great prowess, then will say
Of you things not to be uttered.
What could be greater pain than this? (36)

By dying you attain heaven;
Conquering, you enjoy the earth.
Therefore, O son of Kunti, rise,
In strength of heart resolved to fight. (37)

Make pain and pleasure, gain and loss,
victory and defeat the same,
Then engage now in this battle.
This way you shall incur no sin. (38)

This buddhi yoga by Sankhya
Is now declared to you–so heed!
Joining this insight to your will,
You shall be rid of karma’s bonds. (39)

In this no effort is wasted,
Nor are adverse results produced.
E’en a little of this dharma
Protects you from the greatest fear. (40)

There is a single, resolute
Understanding here, Arjuna.
The thoughts of the irresolute
Are many-branched, truly endless. (41)

They, the ignorant ones, proclaim
Their flow’ry speech, O Pritha’s son,
Delighting in the Veda’s word,
And saying: “There is nothing else.” (42)

Filled with desires, intent on heavan,
Off’ring rebirth as actions’ fruit,
Addicted to so many rites,
Whose goal is enjoyment and power. (43)

Attached to pleasure and power
Their minds are drawn away by this
Speech, and to them is not granted
The insight from meditation. (44)

The Vedas deal with the gunas;
Free yourself from them, and be free
From the pairs of opposites, and
Eternally fixed in the self. (45)

For the Brahmin who knows the self
The Vedas are of no more use
Than a reservoir of water
When there is a flood ev’rywhere. (46)

Your right is to action alone,
Not to its fruits at any time.
Never should they move you to act,
Or be attached to inaction. (47)

Then being steadfast in yoga,
Without attachment do actions
Heedless of success and failure–
Equanimity of mind is called yoga. (48)

Action’s inferior by far
To Yoga of Intelligence.
Seek refuge in enlightenment,
Abhor action done from desire. (49)

Joined to enlightenment, cast off
In this world good and evil deeds;
Therefore to yoga yoke yourself!
For skill in action is yoga. (50)

Those whose minds are joined to wisdom,
Having abandoned action’s fruit,
Are freed from bondage to rebirth
And go to the place free from pain. (51)

When your intelligence crosses
Beyond delusion’s confusion,
Then you shall be indifferent
To the heard and the to-be-heard. (52)

When your intellect stands, fixed in
Deep meditation, unmoving,
Disregarding Vedic doctrine,
You’ll attain self-realization. (53)