Consider a sculptor attacking granite with hand tools. Granite resists such attack violently; it is a hard material, so hard it is difficult to do anything bad in it. It is not easy to do something good, but it is extremely difficult to do something bad. Plastilina, though, is a different matter. In this spineless material it is extraordinarily easy to do something bad–one can do any imaginable variety of bad without half trying. The material itself puts up no resistance, and whatever discipline there is the artist must be strong enough to provide.