  Psillos (1995) argues that any form of structural realism must presuppose a distinction between the form and content of a theory, and/or a distinction between our ability to know the structure and our ability to know the nature of the world. Both these distinctions are illusory according to Psillos because the scientific revolution banished mysterious forms and substances that might not be fully describable in structural terms. For Psillos, properties in mature science are defined by the laws in which they feature, and “the nature and the structure of a physical entity form a continuum” (1995). Hence, for Psillos, structural realism is either false or collapses into traditional realism. (This is the response of Richard Braithwaite (1940, 463) to Eddington's structuralism.) Similarly, David Papineau argues that “restriction of belief to structural claims is in fact no restriction at all” (Papineau 1996, 12), hence structural realism gains no advantage over traditional realism with the problem of theory change because it fails to make any distinction between parts of theories that should and should not enjoy our ontological commitment. Kyle Stanford (2003, 570) also argues that we cannot distinguish the structural claims of theories from their claims about content or natures.