Arjuna opens chapter seventeen with a question the previous chapter provoked. What is the standing of people who sacrifice with faith but set aside the injunctions of scripture? The chapter has just made scripture the measure of conduct, and he wants to know where sincere but irregular practice falls.
The answer relocates the question. The faith of embodied beings is of three kinds, born of their own nature, and it is threefold according to whether clarity, energy or inertia predominates. The faith of each person, the chapter says, conforms to their essential character; a person is made of faith, and whatever their faith is, that is what they are.
That last statement is unusually strong. It does not say that people have faith or lack it, or that faith is correct or mistaken. It says faith is constitutive, and that its colour follows the constitution of the person holding it. Those of clarity worship the gods, those of energy worship spirits of power and wealth, those of inertia worship the departed and hosts of the dead. The classification is descriptive and it is not framed as a moral condemnation of the third group, although the chapter is clearly ranking them.
What makes this chapter valuable to a reference work is that it is the Gita's most direct treatment of religious diversity within a single society. It does not explain the varieties of worship by doctrine, by revelation or by error. It explains them by temperament, and it holds that a person cannot simply adopt a different faith by deciding to, since the faith follows the nature and the nature is what practice slowly changes.