Conversation so far:
What is most important about Hume's academics?
Hume's writings on ethics began in the Treatise and were refined in his An Enquiry Concerning the Principles of Morals (1751.
What were the Principles of Morals?
It is not knowing that governs ethical actions, but feelings.
Are there any other parts of the Morals?
Morals excite passions, and produce or prevent actions.
Reason itself is utterly impotent in this particular.
Was this from a book Hume's wrote?
An Enquiry Concerning the Principles of Morals .
What else did he write?
Hume's theory of ethics has been influential in modern day meta-ethical theory, helping to inspire emotivism, and ethical expressivism and non-cognitivism.
Does he discuss emotivism?
CANNOTANSWER.

Question: What are Hume's theory of ethics?
Self-contained rewrite: What are ethics of Hume's theory?