Full Idea
As the orthodox terms 'thoughts' and 'judgments' are equivocal, since they may equally well denote 'thinkings' as 'what-is-thought', the 'accusatives' of acts of thinking have come to be called 'propositions'.
Gist of Idea
'Propositions' name what is thought, because 'thoughts' and 'judgments' are too ambiguous
Source
Gilbert Ryle (Are there propositions? [1930], I)
Book Reference
Ryle,Gilbert: 'Collected Essays 2 1929-1968' [Routledge 2009], p.16
A Reaction
I have understood propositions to be capable of truth or falsity. 'What is thought' could be a right old jumble of images and disjointed fragments. Propositions are famous for their unity!