For the spiritophiles, of which there are many, here.
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http://space.newscientist.com/article/mg19726401.400-the-hunt-for-the-ununiverse...
The hunt for the Un-universe
a.. 25 January 2008
b.. From New Scientist
c.. Zeeya Merali

Rumsfeld famously distinguished between "known knowns", "known unknowns" and "unknown unknowns". It's a distinction that should ring
clear bells with Harvard physicist Howard Georgi, because he's choosing to make the same distinction between different types of
matter.
Most of us are familiar with the "known knowns" of matter - ordinary stuff, such as tables, chairs, quarks and electrons. Many
physicists spend their days hunting for "known unknowns", like the Higgs boson and the particles that make up dark matter. But
Georgi has gone a step further. He is dabbling in the world of the "unknown unknowns" by proposing the existence of an entirely new
type of matter unlike anything we have encountered before. He calls it the unparticle.

Unparticles are slippery customers. Breaking all the rules that constrain normal particles, they can shift identity and masquerade
as fractions of particles. "It's very difficult to even find the words to describe what unparticles are, because they are so unlike
anything we are familiar with," says Georgi. If his ideas are correct, unparticles exist all around us. They could even exude their
own "ungravity" force, which could replace dark matter as a way of explaining some of the universe's mysteries.