Full Idea
I assume that the contents of thought can be accounted for by appeal to just two general sorts of ingredient - properties (including relations) and indexicals.
Gist of Idea
All thought represents either properties or indexicals
Source
Laurence Bonjour (In Defence of Pure Reason [1998], §6.7)
Book Reference
Bonjour,Laurence: 'In Defense of Pure Reason' [CUP 1998], p.180
A Reaction
I don't accept that relations are a type of properties. Since he does not include objects or substances, I take it that he considers objects to be bundles of properties.