Full Idea
For Stoics, all human impressions differ from animals in that they are rational. …They are impressions that something is the case, and hence are true or false. Their formation involves the use of concepts, and are thus also called 'thoughts' [noeseis].
Gist of Idea
Humans have rational impressions, which are conceptual, and are true or false
Source
report of Stoic school (fragments/reports [c.200 BCE]) by Michael Frede - A Free Will 3
Book Reference
Frede,Michael: 'A Free Will' [Univ of California 2011], p.37
A Reaction
This is a pretty accurate account of my notion of a 'proposition'. Since many animals make judgements, I take them to entertain non-verbal propositions. I assume there are also propositions which are more internal, and thus not 'impressions'.