An Enquiry Concerning Human Understanding

How does Hume make clear distinctions between thoughts and ideas and the phenomena that he calls impressions? Why are impressions the foundation and source of knowledge as opposed to thoughts and ideas?

How does Hume divide moral philosophy into two? Why does he feel that society sees a person who values the abstract and obscure as useless?

Why are cause-and-effect relationships often erroneous? How does habit or custom work to make people believe in a causal connection between two things? Why does Hume refute ancient philosophers and argue that effects are not inferior to causes?