‘Gilding or staining’ the world with ‘sentiments’ and ‘phantasms’

Hume’s ‘science of human nature’ is meant to explain, in theory, how human beings come to have all the ideas, thoughts, and beliefs that we know they have. All such mental items are to find their source, one way or another, in experience. But given Hume’s conception of perception and feeling, and his understanding of the relation between perception or feeling and the rest of our mental life, there is an important class of thoughts which present a special problem for him.