What is the difference between a sentence-type and a proposition? In the literature, sometimes they are used synonymously, sometimes they are differentiated. I can not, for the life of me, figure out what the fundamental difference is, if any. That is, are both bearers of truth? Are both considered abstract objects (nominalists excluded, of course). If they are different, then how are they related to each other, and how are they related to sentence-tokens?
Please shed some light on this issue. Thanks.