Full Idea
Tropes are (says Campbell) substances (in Hume's sense), and indeed resemble his impressions conceived realistically rather than idealistically.
Clarification
'Impressions' are raw simple experiences
Gist of Idea
Tropes are like Hume's 'impressions', conceived as real rather than as ideal
Source
J.P. Moreland (Universals [2001], Ch.3)
Book Reference
Moreland,J.P.: 'Universals' [Acumen 2001], p.53
A Reaction
An interesting link. It doesn't get rid of the problem Hume has, of saying when two impressions are the same. Are they types or tokens? Trope-theory claims they are tokens. Hume's ontology includes 'resemblance'.