Chapter 15 is one of the rarest pieces of literature available in the world that so directly indicates the Supreme and discusses the nature of the Self, with its implications. No other chapter in the Gita stands in favourable comparison.
Chapter 16 addresses the concern of seekers as to what qualities to adopt and what to abandon. It guides man from self-gratification to egoless perfection.
Chapter 17 is a thorough exposition of faith, in the various fields of man's endeavours. The Lord avers that sattvic faith alone leads us to perfection, even if we do not know the Scriptures.
Chapter 18 indicates how the three personalities - sattvic, rajasic and tamasic in their variations create differences among individuals, in sacrifice, wisdom, actions, fortitude and happiness. The chapter is a report on the Bhagavad Gita in retrospect.