Tabula Rasa - blank slate. We are born with no concepts at all, they are derived from our senses.
John Locke's An Essay Concerning Human Understanding looks to refute the concept of innate ideas.
Concept formation is crucial to knowing about the world. It allows us to be concious of things eg. a cup of tea without having to experience the tea at the present moment.
Hume An Enquiry Concerning Human Understanding distinguished impressions and ideas. Impressions.
Impressions are more vivid and more forceful. Hume divides them into sensations and reflections. Sensations deriving from our sense and reflections deriving from our inward feelings from our mind. Ideas are faint copies of impressions and less vivid and forceful. It easier to make mistakes with ideas.
Simple ideas and complex ideas - Simple consists of one element. eg the colour red. Complex consist of several elements eg. a painting.
There are some ideas that do not correspond to our sense experience eg. a unicorn.
A unicorn is derived from a variety of simple ideas - a horse and a horn. No idea, no matter how abstract or complicated it may be comes from anything but a combination of our sense experiences.
Hume makes a point of saying that our complex ideas are not copies of our impressions. Only simple ideas are. All ideas can be analysed into simple ideas which come from empirical experience.
This explains how we have concepts of things that we seemingly have not experienced
GOD - our experience of power, goodness and benevolence + our idea of unlimitedness.
MORALITY - our concepts of good and bad cannot be traced back to any particular sensation. We get these from our inner sensations, our emotions, on how certain actions make us feel.