Dualism
"Dualism, the view that reality consists of two disparate parts. The crux of dualism is an apparently unbridgable gap between two INCOMMEASURABLE ORDERS OF BEING that must be reconciled if our assumption that there is a comprehensible universe is to be justified. Dualism is exhibited in the pre-Socratic division between appearance and reality; Plato's realm of being containing eternal Ideas and the REALM OF BECOMING CONTAINING CHANGING THINGS; the medieval division between finite man and infinite God; Descartes's substance dualism of thinking mind and extended matter; Hume's separation of fact from value; Kant's division between empirical phenomena and TRANSCENDENTAL NOUMENA; the epistemological double-aspect theory of James and Russel, who postulate a neutral substance that can be understood in separate ways either as mind or brain; and Heidegger's separation of being and time that inspired Sartre's contrast of being and nothingness..."
[The most egregious horseshit emphasized by yours truly.]
Suddenly, I remembered why I never studied philosophy. Good ideas, but the mumbo jumbo is an actual impediment to the transmission of those ideas.
The first two sentences of Cambridge's entry can be summarized as follows: there is a split between subject and object. That's it!
Further commentary provided for those schools that I'm slightly familiar with, that I think can be simplified in layman's terms:
Plato - perfect knowledge (Forms) vs. imperfect beliefs/opinions (material world)
Descartes - we could be just brains in a vat, but God assures us that the relationship between our senses and what they perceive is real
Kant - we could be just brains in a vat, but something other than God (a thought process, I guess; "noumena") assures us that the relationship between our senses and what they perceive is real
Heidegger - okay, I've read Heidegger, and I still don't see what the big deal is,other than a truly exceptional talent for horseshitting. Sure, he talks about being and time, but in order to figure that out, I the reader had to put in as much creative energy into it, interpreting, as the philosopher did, writing. (There's another philsophical phenomenon for you.)