 A lot of our reasoning seems to involve projecting observed patterns onto unobserved instances. For example, suppose I don’t know whether the coin I’m holding is biased or fair. If I flip it 9 times and it lands tails every time, I’ll expect the 10th toss to come up tails too. What justifies this kind of reasoning? Hume famously argued that nothing can justify it. In modern form, Hume’s challenge is essentially this: a justification for such reasoning must appeal to either an inductive argument or a deductive one. Appealing to an inductive argument would be unacceptably circular. While a deductive argument would have to show that unobserved instances will resemble observed ones, which is not a necessary truth, and hence not demonstrable by any valid argument. So no argument can justify projecting observed patterns onto unobserved cases. (Russell and Restall (2010) offer a formal development. Haack (1976) discusses the supposed asymmetry between induction and deduction here.)