Answer:
A strong conviction.
Step-by-step explanation:
Generally, the term 'avid' can be understood as having a deep or keen interest in something or someone. It is simply holding a firm desire or enthusiasm towards a particular thing.
To define the term 'avid' according to the context clues, it could be understood as the act of having a strong conviction towards a particular set of beliefs or ideas.
This can be inferred from the fact that Ralph Waldo Emerson's keen interest in Hindu philosophy. It had influenced him so much that it had changed his conviction about humans and the universe.