Try http://www.geom.umn.edu/zoo/toptype/klein/standard/
It contains a graphic plus the text:
This is an image of the Klein Bottle. It contains one closed, continuous
curve of self-intersection, where the "tube" meets the "bottle". In this
picture, it is where the yellow part meets the dark blue part. The image
self-intersection is a circle.
The relevant point is that though there seem to be an
"inside" and an "outside", there is really only one side.
Like the Mobius Strip, to which it is related. (The
Klein Bottle can be constructed by connecting two Mobius
Strips.) So I'm trying to say that the distinction
between objective and subjective phenomena is similarly
an illusion. There is one "reality" which has these
different aspects, or you might call them abstractions.
It's like objective phenomena are on the outside of the
bottle, and subjective ones on the inside, but in fact
the distinction is merely relative. All there really is
is experience -- what's experienced (objects), and
what experiences (subjects) are abstractions. The
distinction is, in many cases, useful -- just as a Klein
Bottle could actually be used to carry water -- but it's
relative, all the same -- it won't carry any real
theoretical weight -- and there are better shapes for
carrying water.
Materialism is based on the subjective/objective
distinction, as it claims that objective phenomena are
real and subjective ones unreal, but it fails to explain
consciousness. Philosophical idealism (subjectivity is
real and objectivity unreal) and dualism (both are real,
though in different ways) also fail for the same reason.
Idealism fails to explain the success of science, and
dualism fails to explain interaction between subjective
and objective phenomena. In all these cases, the
mistake is to assume a fundamental difference between
subjectivity and objectivity.
-- Robin