Six of them are unfinished four Prisoners (a.k.a.The Slaves), St. Matthew, and a Piet?  each a fascinating revelation of how Michelangelo released their power from the marble.
Most of Michelangelo's marble sculptures are still unfinished.
mnli hypothesis: Most of Michelangelo's marble sculptures are still unfinished. premise: Six of them are unfinished four Prisoners (a.k.a.The Slaves), St. Matthew, and a Piet?  each a fascinating revelation of how Michelangelo released their power from the marble.