Chapter 18 is about bondage and liberation, and the means of liberation. A jīva is said to be in bondage if he is tied up by the noose of the eightfold primary tattvas: prakṛti etc. When freed from them he is called liberated. Perfect control and subjugation of prakṛti and its offshoots is mokṣa (salvation). A jīva when freed from bondage is called a liberated soul. The set of eight that binds is: prakṛti, buddhi (cosmic intellect), ahaṁkāra (cosmic ego) of the nature of attributes, and the five tanmatras—the cosmic principles of earth, water, air, fire and space.