Truth that is naked is the most beautiful, and the simpler its expression the deeper is the impression it makes.
Mysticism & Schopenhauer
Additionally, Schopenhauer sometimes himself goes beyond reason to a ‘mystical’ point of view:
"The thing in itself, which we know most immediately in the will, may have, entirely outside all possible appearance, determinations, qualities, and modes of existence which for us are absolutely unknowable and incomprehensible, and which then remain as the inner nature of the thing in itself." (Schopenhauer, vol.2, p.198)
"… in his later writings there are passages which suggest that the thing-in-itself is will in only one of its aspects, and that it has other aspects that are the focus of mystical awareness." (Nicholls 1999)
The man in whom the denial of the will-to-live has dawned, however poor, cheerless, and full of privation his state may be when looked at from outside, is full of inner cheerfulness and heavenly peace. (…) Nothing can distress or alarm him any more; nothing can any longer move him; for he has cut the thousand threads of willing which hold us bound to the world and which as craving, fear, envy, and anger drag us here and there in constant pain. He now looks back calmly and with a smile on the phantasmagoria of this world which was once able to move and agonize even his mind, but now stands before him as indifferently as chess-men at the end of a game, or as fancy dress cast off in the morning, the form and figure of which taunted and disquieted us on the carnival night. Life and its forms merely float before him as a fleeting phenomenon, as a light morning dream to one half-awake, through which reality already shines, and which can no longer deceive; and, like this morning dream, they too finally vanish without any violent transition.