The fourth chapter is titled ‘Yoga in the Bhagavad-gītā’; yoga no doubt occupies a central place in the Gītā and is one of the fundamental constituents of its structure; the chapter is engaged with dhyāna-yoga, which in many ways resembles Patañjali’s classical yoga system. While the Gītā tends to use the term yoga interchangeably with karma-yoga, and while the text focuses primarily on karma-yoga, jñāna-yoga and bhakti-yoga, the techniques of Patañjalian-type yoga are outlined throughout the entire sixth chapter, albeit subsumed under devotion to Kṛṣṇa. This chapter indeed takes the Yoga-Sūtra or similar such ideas as a point of departure, highlights its similarities to dhyāna-yoga and argues that the Gītā not only maintains similar views but expands and elaborates them. As opposed to the very concentrated and internalized mode of yoga articulated in the Yoga-Sūtra, themes and ideas that are described in the Yoga-Sūtra in a concentrated sūtra style receive a more elaborate description in the Gītā. These core doctrines are expanded and present in all other three yoga paths, that is, karma, jñāna and bhakti. As such, a study of these core yoga concepts, such as the ladder principle, mental restraint and samādhi, is required in order to understand the other three paths presented in the Gītā.