 There are a number of complications with this way of motivating presentism. For one thing, although it’s typical (in metaphysics) to see appeals to ontological parsimony in cases where one view is more “qualitatively” parsimonious than its rivals, that is, cases where a view posits fewer kinds of thing than opposing views, it’s far less typical to see appeals in cases where one view is merely more “quantitatively” parsimonious than rivals, that is, cases where a view posits fewer things than another. The fact that appeals to quantitative parsimony are less typical reflects a general attitude that the only ontological parsimony that one ought to respect is qualitative parsimony. As David Lewis famously puts it: