In the initial experiments, Ves manipulated Peter Seterin's spiritual potential like a mortician dissecting a corpse.
He knew what he was doing was wrong and unnatural in a way, and the increasing resistance he encountered only reinforced that impression.
Peter Seterin was alive. His spirituality, however weak it may be, represented his strength as a person and a living, sentient being.
From his various interactions with other spiritual entities such as his spiritual products, he always made a big distinction between their states before and after Ves breathed them to life.
As long as they hadn't come into existence, spiritual products remained a disparate collection of ingredients. Ves could tinker with the ingredients and manipulate their merger process to an extensive degree.