 The account takes Pasnau’s original insight that sounds be considered as akin to colors in their being located features of objects. Indeed, Kulvicki draws a set of analogies between sounds and colors based on the assumption that colors are dispositions to reflect light in a certain manner. The analogies include the fact that as colors exist in the dark (being dispositions) sounds exist in the vacuum, and that as light waves are a way to get knowledge of colors, compression waves in a medium are a way to get knowledge of sounds. To complete the analogy, as “colors give off light when stimulated by light, objects in a medium give off compression waves when they are thwacked” (2008: 4). More controversially, “Without vibrating, objects have sounds, but these sounds cannot be heard” (2008: 4). Thwacking is the key element in the dispositional proposal. Thwacking reveals sounds. A good thwack (an impulse that contains all relevant frequencies) is considered to be to sounds what white light is to colors. White light contains waves of all lengths in roughly the same proportion and thus samples adequately the dispositions of the object to reflect some of them. If you lit up a surface with a monochromatic laser beam at 500nm, the disposition the surface may have to reflect light of 600nm will not be revealed. A good thwack makes the object resonate at all frequencies and thus reveals the vibratory modes of an object by stimulating it at the frequencies at which it responds better.