What is the 'Unmanifest' or 'causal body', and how can it be overcome to achieve liberation?

According to the teachings in Chapter 50, the 'Unmanifest' (Avyakruta) is also known as the 'causal' (karana) body of the soul. It is described as being with the reflection of consciousness and is the very cause of pure ignorance. This ignorance of the Soul is the source of the causal body. The text states that the only way to remove this body is through the knowledge of the unity of Brahman and the Soul. When this unifying knowledge is realized, ignorance is removed, which in turn removes the causal body. This state of 'abiding in one's own form' is what is given the name 'liberation' or Moksha.