 That, however, is not true of the objects—the paramecia, say—that are purportedly being observed through the microscope. Because the paramecia are not directly observable without instruments, we can only hypothesize that there are objects being observed for which the invariant geometric relations hold. It is possible for us, then, to maintain an agnosticism about the paramecia that we can’t about the tree (160). We can regard our observations via the microscope the same way we regard our observations of rainbows—namely, as observations of phenomena that are public (even capable of being captured by photographic equipment) without at the same time being observations of some existent object (162). (We say that the rainbow is not an actual physical object because it does not participate in the invariant geometric relations we expect of actual physical objects: “If the rainbow were a thing, the various observations and photos would all locate it in the same place in space, at any given time” (157) ).