Here Bryan Magee gives some background on Schopie, which leads into an interview with philosophical historian (and Jesuit priest, known for debating Bertrand Russell on the radio re. the existence of God) Frederick Copleston:
At the end of this first clip, Copleston points out that Kant thought of things in themselves as plural: there's the table as you see it, and the table in itself, whereas Schopenhauer thought that if you take away space and time, you can't have multiplicity: the object as it is in itself, not conditioned by these things, must be one. We are all one. This reflects his interests in the Hindu Upanishads, which apparently he read frequently and helped with a translation of.
This thought is continued in part two:
Watch on youtube.
Magee ties this thought in not only with Hinduism but with Buddhism, but says that Schopenhauer derived this conclusion from Western sources and found that it coincided with Eastern thought, as opposed to being impressed by Eastern thought and cramming this into his Kantian, as I posited on the episode.
The discussion continues through a few more clips, with some more detail than we gave on "will" than we really went into. Magee describes Schopenhauer's picture of reality as underlyingly will as translatable into saying that it's underlying energy. In other words, modern physics supports Schopenhauer, and he can't be scientifically brushed away as I did in pointing out his connections to vitalism. Listening past this, the discussion gets into his pessimism and other areas that we didn't cover at all in the episode.