Determinable Properties and Overdetermination of Causal Powers

Do determinable properties such as colour, mass, and height exist in addition to their corresponding determinates, being red, having a mass of 1 kilogram, and having a height of 2 metres? Optimists say yes, pessimists say no. Among the latter are Carl Gillett and Bradley Rives who argue that optimism leads to systematic overdetermination of causal powers and hence should be rejected on the grounds that the position is ontologically unparsimonious. In this paper I defend optimism against this charge by showing that overdetermination of causal powers cannot plausibly be avoided when grounding what I call joint powers. It is therefore not clear why the optimist should be worried about the overdetermination of causal powers that follows from positing determinable properties.