  Although Locke mentions only secondary qualities here, his point presumably applies to all sensations, including our sensations of macrolevel primary qualities, such as the shape and size of a snowball or lump of gold. For again, genuine knowledge is knowledge of necessary connections, with the conceptual relations in geometry being the model, and it does not seem possible to discover such connections between any sensation and the sizes, shapes, and textures that are supposed to cause them. Despite the resemblance of macrolevel primary qualities to microlevel ones, both being of the same  type,[19] the idea of a quality is nonetheless a very different thing than the quality itself.