 It may be helpful to mention several things that are not included in the above. Sense data are described as immediate objects of awareness, but there is no statement that we therefore only immediately perceive sense data and do not immediately perceive external objects, a conclusion which many theorists accepted. Further, there is no specification of whether sense data are two dimensional or contain depth. Early theorists are typically read as asserting two-dimensional  data;[2]  the second wave, including Price (1932: 3, 218–220), explicitly gave some of them depth. There is no statement about whether sense data persist beyond the momentary sensing of them, as there was disagreement on this point. There is no assertion of their origin, causal or otherwise. It is natural to think of sense data as caused by objects and as being related to those objects as appearance to reality, a position expressed by some authors (e.g., Russell 1912: ch. 1; Broad 1923: 237–240). But that conception is not included here in the agreed-upon attributes of sense data in their early history. Similarly,  item 5  distinguishes the apprehension of a sense datum from that of a material object or other entity; it takes no stand on whether such objects are inferred from sense data, are affirmed by a cognitive act that is not an inference, or are treated in some other way. Nor does item 5 say whether sense data represent objects or their properties, independently of a further act of judgment or affirmation; some classical theorists denied that sense data are intrinscially representational. Further, sense data were not tied to specific neurophysiological processes, even if it was admitted by some authors that they are conditioned by neurophysiological states (such as those that produce afterimages). Finally, naïve realists sometimes described the immediate apprehension of a portion of the surface of an object as a perceptual datum. Present-day taxonomies of philosophies of perception typically contrast naïve direct realism with sense-data theory, an outlook that results in part from the present tendency to treat sense data as mental (Crane &amp; French 2015 [2021]). But in the classical period, there were arguments to the effect that sense data are direct perceptions of a part of the surface of a material object (Moore 1918–19: 23–24), a position that Price (1932: chs. 2–3) described and sought to undermine.