According to Wright there exist cornerstone propositions—or simply cornerstones—for different areas of discourse. In accordance with Wright’s characterization of it, c is a cornerstone for an area of discourse d just in case for any proposition p belonging to d, p could not be justified for any subject s if s had no independent justification for accepting c (see mostly Wright 2004).[10] Cornerstones for the area of discourse about perceivable things are for instance the logical negations of sk