 The intentional content—the external reference—of a perceptual experience is in a certain sense based upon sensa (thought not in the sense that there is a train of swift inference leading from the presence of a sensum to the mind to a certain perceptual belief). (1923, pp. 246–7.) It is this content which represents the environment as featuring a physical object so-and-so. Sensa are clearly incapable of carrying such content. Furthermore, from the very nature of the case the general notion of physical object “cannot have been derived by abstraction from observed instances of it, as the notion of ‘red’ no doubt has  been.”[9]  In fact, general concept of a physical object “is not ‘got out of’ experience until it has been ‘put into’ experience. It is best described as an innate principle of interpretation which we apply to the data of sense-perception” (1925, p. 217).