It is clear that the mass of the valence quarks is only a small fraction of the mass of the hadrons (for example, the proton). However, I wonder if it would be possible to get massive protons in QCD if the quarks were truly massless. On one hand, for massless quarks, the pions, as Goldstone bosons of an exact Chiral symmetry, would be massless. On the other hand, the binding energy of any electron-positron bound state would vanish in the limit of zero electron(positron) mass. Is there some general argument to exclude in QCD finite masses for systems of masless quarks? In the case of glueballs (made of massless gluons), do they have finite mass?