Full Idea
Schopenhauer radically departs from his fellow idealists in his assertion of the irrational character of reality.
Gist of Idea
Schopenhauer, unlike other idealists, says reality is irrational
Source
report of Arthur Schopenhauer (The World as Will and Idea [1819]) by Peter B. Lewis - Schopenhauer 4
Book Reference
Lewis, Peter B.: 'Schopenhauer' [Reaktion Books 2012], p.96
A Reaction
This is the rejection of the original confidence about rationality of the stoics. And yet Schopenauer saw the principle of sufficient reason as axiomatic. Not sure how to reconcile those. Lewis identifies this idea as 'Romantic'.