Explain the empiricist distinction between simple and complex concepts.

Empiricism is the view that knowledge is acquired through sense experience. According to Hume's empirism, concepts or 'ideas' are formed in the mind from directly perceived impressions. These concepts are further divided into complex ideas, which can be broken down into their constituent parts. Simple ideas are those concepts that cannot be broken down any further into more basic concepts.

A simple idea corresponds to an impression, and we cannot have one of these concepts without having had an experience of it beforehand. Complex ideas can be formed from relevent impressions, without having had an experience of the exact concept. For example, the colour red is a simple idea as we cannot conceive of two or more separate ideas that form the concept of the colour red. A red chair is a complex idea, as we can conceive the colour red and the concept of a chair as separate from each other. Furthermore, we can have the idea or concept of a red chair without having ever seen a red chair, but having experienced the colour red and seen a chair and combining these two concepts.