The thirteenth chapter is the beginning of the third ṣatkam of Bhagavad Gita.

In the first ṣatkam, Lord Krishna highlighted karma yoga, in the second ṣatkam, Krishna highlighted Upasana yoga and in the third ṣatkam Krishna is going highlight jñāna yoga.  The first three chapters, that is chapter 13, 14 and 15, are very important from the philosophical angle, as the entire upanishad sara is given in these chapters. These chapters highlight drk drsya viveka, the knowledge that clearly distinguishes the difference between Purusha and Prakriti.

In the first verse Arjuna asks for clarification regarding six technical terms appearing in the scriptures.  These topics are:

1. kṣetram
2. kṣetrajña
3. jñeyam
4. jñānam
5. Prakriti
6. Purusha

Kṣetrajña, purusha and jñeyam are all refer to atma.  The words kṣetram and prakriti refer to anatma.  jñānam remains separate.  Thus, the six topics are reduced to three topics:  Atma, Anatma and jñānam.

Anatma

In verses 2 to 24, Lord Krishna describes Anatma.  Anatma is Chethanam plus Prakrithi.  Whatever I experience is anatma.  The entire universe will fall under anatma.  Anything objectifiable is anatma.  The body comes under anatma, because we experience the condition of the body.  The mind also comes under anatma, because we experience the condition of the mind.  The world, body, and mind along with all their different conditions is anatma.  Nature of anatma:

• Made up of matter and is inert in nature.  The sentiency of the body is not intrinsic to the body but borrowed from the atma.  The mind is also material.
• Full of attributes; sagunam, endowed with varieties of properties.
• Subject to constant fluctuations and modifications.

Because of the changing nature, it undergoes the condition and becomes visible and manifest.  Maya is unmanifest universe.

Atma

Atma is kṣetrajña, purusha and jñeyam.  If the whole universe falls under object of experience, then experienced universe pre-supposes the presence of an experience or subject.  Every object presupposes a subject.  Atma is Chethanam and Purusha.  This unobjectifiable experiencer principle is atma.  Features of I, the atma the consciousness principle:

• Not a part, product, or property of the body
• Independent entity pervading and enlivening the inert body
• Not limited by the boundaries of body
• Will continue to exist even after the fall of the body.  Mortality is the feature of the body, not of the atma.  Atma is immortal.
• Atma continues after the fall of the body, but not available for transactions because a medium is not available.

Atma/Consciousness can be compared to space and sunlight:

• They are all one (ekam)
• They can’t move
• They are indivisible
• Can’t be contaminated or polluted
• Support of everything
• Illuminates everything.

Jñānam

Dharmic values and study of scriptures is required for jñānam.   Dharmic values must be assimilated in mind and a mind with dharmic values is needed for jñānam.  The dharmic values are moral values and are fourfold qualifications.  These fourfold qualifications or sädhana catuṣṭaya saṃpatti are:

• Discrimination:  Understanding that the world can’t give security; that can come only from nithya vasthu the ever-present Brahman. 
• Dispassion:  Changing the priorities of life from world to Brahman.
• Discipline:  Integration of the entire personality with Atma jñānam.
• Desire:  For moksha or jñānam

These four are expanded into 20 terms in verses 8 to 12 of this chapter.

Verses 25 to 35:  jñāna sadhanam and jñāna phalāḥṃ; Stages to obtain this knowledge and benefits of this knowledge.

• Karma yoga to remove impurities
• Upasana to remove restless mind; extrovertedness of mind, so mind will become tranquil and focused.
• Sravanam:  consistent and systematic study of Vedantic scriptures under the guidance of a competent guru.
• Mananam:  Raising doubts and clarifying doubts
• Nidhithyasanam:  Dwelling on the vedantic scriptural teachings.

Benefits of the knowledge:

• Freedom from raga and dwesha; freedom from attachments and aversion
• Immortality of atma; not afraid of mortality
• I come to know I am neither the kartha and boktha
• Brahmatvam: I am limitless.

In simple language, jivan mukthi is the benefit.  This knowledge takes from bondage to liberation.