 An impression of a square, which we are conscious of as extended, is really extended. Our consciousness of sensory properties, as those properties are present to us phenomenally, reveals the properties as they are. We can’t be mistaken about them. Items 3 and 6 are affirmed by Hume. Indeed, substituting “impression”, “idea”, and “perception” for “sense datum”, we might ascribe to Hume all of the items in the Classical Notion, save perhaps  item 8,  the act-object relation. In reading the Treatise and Enquiry, one might be tempted to ascribe item 8 to Hume, but he notoriously rejected such ascriptions in the Appendix to the Treatise.