A quark is the four dimensional pixel defining the resolution of reality. When it's "off" it's potential; when it's "on", it's material, and, depending on which are "off" and "on" in the matrix of all quarks, determines what element is present by determining which atom is represented.
Whether a quark is "off" or "on" is controlled by (not the conscious) mind. This is why it's impossible to measure measurements.
So there.
For Lurkers who want to know what a quark is, etc. - here's a very easy-to-digest summary from Fermilab: