Just a random early-morning thought
According to my brand of existentialism...
There is no such thing as reality or illusion. That which has been perceived has reached the height of reality. There are other people besides me, but they are no more "real" than chimeras. However, I acknowledge that those people significantly impact the reality that I perceive, and so I ascribe to them especial importance among the things I perceive. "Reality" is in fact a set of perceptions shared by myself and other perceptions of mine: that is, other people. Illusion are those perceptions which cannot be confirmed by my sentient perceptions. A "level" of reality may be assigned by asking the question: with how much of my perceived reality can this perception interact? For instance, if a Chimera passes through (perceived) rocks, trees, etc, it obviously has a lower "reality" than that which freely interacts with everything else--that is, nearly all physical objects. It is worthy of note that this assigns as a rather low level of reality to God.
I call this a stick philosophy. I have it around to use in arguments and debates, but I would never use it practically. I have to admit, though, that I'm rather fond of existentialism.
Dan