In 1.3.9, Hume introduces two levels of reality. He does this to show why the relations of resemblance and/or contiguity cannot reflexively produce vivacious ideas in the manner that causation can (T 1.3.9.2; SBN 107). But the implications of Hume's account of reality are far-reaching. In fact, if we don't take his two systems of reality into account, we can't understand his notion of an object, his many forms of belief, nor his notion of justification. Oddly though, Hume's two systems of reality are largely overlooked in Hume scholarship, if not ignored altogether (with some exceptions, e.g. Kemp Smith 1941; Owen 1999; Loeb 2002).