Why is a Guru considered so important for removing ignorance, even for someone who is already knowledgeable?

Chapter 50 emphasizes that a Guru is indispensable because ignorance often manifests from doubt, which even a wise person can fall prey to. The text gives the example of the supreme knower Shuka, who 'suffered loss due to doubt (vikalpa).' It powerfully illustrates this by comparing doubt to a single drop of fermented gruel that ruins a large pot of milk. Therefore, the role of the Guru is to help remove this corrupting doubt. By first understanding and removing ignorance with a Guru's guidance, the mind is purified, which allows for infinite 'knowledge' to manifest and non-dual Samadhi to be attained.