What is the primary obstacle preventing people from attaining liberation, and how is liberation itself defined?

According to the teachings in Chapter 50, the primary obstacle to liberation is ignorance, referred to as Avidya. This ignorance is the cause of the 'causal' body and creates the delusion that leads one to identify with the physical self and worldly attachments, such as thinking, "I am the body, mine are wife and home." Liberation, or Moksha, is defined very specifically as "abiding in one's own form." The text is clear that this is the only true liberation. Therefore, to achieve Moksha, one must first remove the veil of ignorance. This removal is only possible through the attainment of knowledge concerning the fundamental unity of Brahman and the Soul, which dissolves the illusion of a separate self.