 What one apprehends must be the real object itself, not “some mental copy” of it, so Cook Wilson is claiming here that, as a state of mind, knowledge contains its object: “what we apprehend […] is included in the apprehension as a part of the activity or reality of apprehending” (SI, 70). A long letter to G. F. Stout (SI, 764–800) is of particular importance here, where Cook Wilson criticized Stout on ‘Primary and Secondary Qualities’ (Stout 1904), with this key diagnosis, of the ‘objectification of the appearing as appearance’: