Namely, the supposition of a simpler, more parsimonious chain of events is preferable to the supposition of a more complicated, less parsimonious chain of events.
A utilitarian (or radical egalitarian) might also claim that their theory is more parsimonious than prioritarianism (which values well-being "and" priority).
For example, parsimony is the best way to produce an evolutionary tree of the species (cladistics), suggesting that parsimonious adaptations are selected.
