Just as a very good sweet will have something hidden inside of it, or a company will have the inner group of key people, the Gita has a core made up of four verses. These are called the Catur Sloki (catur = four, and sloki = verses), and they summarize the entire Gita.
The eighteen chapters of the Gita are themselves divided into 3 parts. The middle six chapters focus on bhakti and are “protected” on either side by teachings on karma-yoga (the first six chapters) and jnana yoga (the focus of th