Complex sentence: The reasons for quark confinement are somewhat complicated; no analytic proof exists that quantum chromodynamics should be confining, but intuitively, confinement is due to the force-carrying gluons having color charge.
Split into simpler sentences: The reasons for quark confinement are somewhat complicated; no analytic proof exists that quantum chromodynamics should be confining. The current theory is that confinement is due to the force-carrying gluons having color charge.