What are the philosophical antecedants for a sortitionally-chosen legislature?
Antecedents go back at least to the first democrats of Athens who wished, by using the lot, to avoid factional domination.
Here are a few others to begin with:
"...We hold these truths to be self-evident, that all men are created equal." -- Declaration of Independence
"... that government of the people, by the people, for the people, shall not perish from the earth." -- Abraham Lincoln
"The most important political office is that of the private citizen." -- Louis D. Brandeis