Schopenhauer' essay "On the Freedom of the Will" won the prize of the Royal Danish Academy of Sciences in 1839. He defined the liberum arbitrium indifferentiae as not being determined by prior grounds. "Under given external conditions, two diametrically opposed actions are possible." On the freedom of the Will, p.8)
"All really deep thinkers of all times, no matter how different their other views may have been, agreed in maintaining the necessity of volitions upon the occurrence of motives, and in rejecting the liberum arbitrium. (On the Freedom of the Will, p.60)
"If we do not accept the strict necessity of all that happens by means of a causal chain which connects all events without exception, but allow this chain to be broken in countless places by an absolute freedom, then all foreseeing of the future, in dreams, in clairvoyant somnambulism, second sight, becomes objective and hence absolutely impossible, and so inconceivable. (On the Freedom of the Will, p.64)
On HegelIn the Monist, volume 14, 1904, Paul Rée wrote an obituary for Schopenhauer.
"Schopenhauer says that when a German hears the word "Idea" unctiously pronounced, his head commences to swim, and he feels as though he was going up in a balloon. This is a very tame description of the sensation one feels, and the mental torture endured by the inquirer, who attempts to hew his way through the jungle of barbarous concepts, out of which is constructed the metaphysical "system" of a Fichte or Hegel; and then alas! to find out that this "system" is a phantasm of the brain, which only explains the sort of head which invented it, but throws no light upon the world we live in."