Which concept is identified in chapter 37 as the root cause for perceiving differences in the world and experiencing worldly worries?

In Chapter 37, the concept identified as the root cause of all worldly worries and the perception of manifoldness is Avidya, or ignorance. This ignorance is what establishes the bonds of worldly attachments, such as to sons and cattle, and causes constant worry day and night. The text further defines Avidya as having only 'Preyas' (the pleasant) as its subject, as opposed to Vidya (knowledge), which concerns 'Shreyas' (the ultimate good). To counter this ignorance, the chapter advises acquiring knowledge through the scriptures and the Guru, which ultimately removes the perception of difference and ends suffering.