 According to Campbell, the world is constituted by a rather limited number of field tropes which, according to our (current) best science, ought to be identified with the fields of gravitation, electromagnetism, and the weak and strong nuclear forces (plus a spacetime field). Standardly, these forces are understood as exerted by bodies that are not themselves fields. Not so on Campbell’s view. Instead, matter is thought of as spread out and as present in various strengths across a region without any sharp boundaries to its location. What parts of the mass field we choose to focus on will be to a certain degree arbitrary. A zone in which several fields all sharply increase their intensity will likely be taken as one single entity or particle. But given the overall framework, individuals of this kind are to be viewed as “well-founded appearances” (Campbell 1990: 151).