 Several threads within early modern theories of perception provide a background for the Classical Notion of sense data. First, there was the already-noted tendency to distinguish sensation from perception, or a passively received sensory core from a further perceptual act. For vision and touch, this further act typically included perception of objects as existing and as present in a locally coherent three-dimensional space. The act might result from judgment, inference, or association. Second, the immediate objects of sensory perception were sometimes rendered as mental representations from which an external world must be inferred, possibly allowing for skepticism about the basis for such inferences. Third, these mental representations might or might not be attributed all or most of the features of the Classical Notion. In particular, many early modern theorists, as many theorists now, distinguished between representation via intentional contents that do not literally possess the qualities they present (such as color or shape), and representation through entities that possess the properties (such as color or shape) as they appear.