Secondary Qualities as Dispositions

In this paper I will defend the view that, according to Locke, secondary qualities are dispositions to produce sensations in us. Although this view is widely attributed to Locke, this interpretation needs defending for two reasons. First, commentators often assume that secondary qualities are dispositional properties because Locke calls them “powers” to produce sensations. However, primary qualities are also powers, so the powers locution is insufficient grounds for justifying the dispositionalist interpretation. Second, if secondary qualities are dispositional properties, then objects would retain secondary qualities while not being observed, but Locke says that colors “vanish” in the dark. Some commentators use this as evidence that Locke rejects the dispositionalist view of secondary qualities, and even those that are sympathetic to the traditional interpretation find these comments to be problematic. By contrast, I argue that even in these supposedly damning passages Locke shows an unwavering commitment to the view that the powers to produce sensations in us, i.e., the secondary qualities, remain in objects even when they are not being perceived. Thus, the arguments against the traditional interpretation are unpersuasive, and we should conclude that Locke does indeed hold that secondary qualities are dispositions to cause sensations in us.