 Thus Hume’s treatment of substance is like his treatment of causation, in that he sees both as the projection onto the world of a tendency of our minds either to pass from one thing to another or to associate them in some way. He either doubts that there are such things as substance or causation (scepticism) or even positively denies that there are (nihilism). Out of Hume’s very forthright negative attitude there developed two more subtle variants. One of these variants is in the empiricist tradition. That tradition modified Hume’s approach by developing it into a form of reductionism. The experiences that gave rise, through habit, to the mistaken belief (in, for example, substance or causation) are presented as what the belief really affirms. That is, the empirical basis for what Hume deems to be an illusion, is reinterpreted as the reductive account of the concept. Causation then becomes constant conjunction, or substance a name for a bundle of properties organised in a certain way or the continuing of the possibility of certain sensations.