Final answer:
In Hume's philosophy, 'ideas' refer to the contents of our memories and imagination, derived from initial sense impressions, in contrast to 'impressions' which are immediate sensations.
Step-by-step explanation:
In David Hume's philosophy, the term "ideas" refers to the contents of our memories and imagination. Contrasted with "impressions", which are our immediate sensations or raw sense data, "ideas" are the less forceful, less vivid products of the mind that come about through reflecting on these impressions. Ideas are derivative; they stem from impressions that have been combined, separated, or manipulated by the imagination, leading to thinking, reasoning, and the formation of knowledge.
Hume states that we have no ideas without initial sense impressions, emphasizing that reason alone (a priori) does not lead to knowledge. In summary, Hume's empirical approach asserts that our knowledge is limited to what we perceive through our senses, which are then recalled and reshaped into ideas by our memories and imagination.