 As Horgan (1984) points out, talk of ‘physical information’ in the context of the knowledge argument is ambiguous between an epistemological and an ontological reading. “Physical information” may be interpreted (a) in the sense of what Horgan calls ‘explicit physical information’ (according to Horgan’s proposal a sentence S expresses explicit physical information about certain processes just in case S belongs to, or follows from, a theoretically adequate physical account of those processes) or (b) in the sense of ‘ontologically physical information’ which is explicated in Horgan (1984, 150) as follows: a sentence S “expresses ontologically physical information about certain processes just in case (i) all entities referred to or quantified over in S are physical entities, and (ii) all the properties and relations expressed by the predicates in S are physical properties and relations.” Presupposing a distinction along these lines one may replace ‘to have all explicit physical information about x’ by ‘to have complete physical knowledge about x’ and one may replace ‘to have all ontologically physical information about x’ by ‘to know all the physical facts about x’. The argument may thus be reformulated in two different ways: