I think the most interesting thing about the Psuke is that it works even though Fane's metaphysics was apparently, in Bakker's words, "the most wrong" of all the systems espoused across Earwa.
Psukhe might not be based on Fanimry metaphysics at all. Fane could've just been in the right circumstances to discover it, subsequently completely misinterpreting or shoehorning it into his worldview.
Right now, for me, Psukhe is pretty much explained by the notion of using emotions to convey meaning. It's like writing a book, only without actually writing it. It's an idea, a feeling, and it's
perfect. An attempt to put this idea, this perfection, into words would inevitably soil it. It's just for you, shining before you mind's eye. You know it, you
feel it, it's real for you without speaking, and so, in Earwa, it happens.
This also ties in to Anagogic sorcery imitating literature (basically, or the art of words in general) or Iswazi imitating sculpture. And there is the whole dichotomy of art and science in Earwan sorcery, with Gnosis being science.