 When we reason a priori, we consider the idea of the object we regard as a cause independently of any observations we have made of it. It can’t include the idea of any other distinct object, including the object we take to be its usual effect. But then it can’t show us any “inseparable and inviolable connection”—any necessary connection—between those ideas. Trying to reason a priori from your idea of an aspirin, without including any information you have of its effects from your previous experience, yields only your simple ideas of its “sensible qualities”—its size, shape, weight, color, smell, and taste. It gives you no idea of what “secret powers” it might have to produce its usual effects. Hume concludes that a priori reasoning can’t be the source of the connection between our ideas of a cause and its effect. Contrary to what the majority of his contemporaries and immediate predecessors thought, causal inferences do not concern relations of ideas.