 As an example, consider the particular doubt about smoke as pervaded by fire. If smoke is not produced from a set of causes excluding fire, then smoke, as not produced from a causal complex including fire, would not be produced (a conclusion in contradiction, presumably, with the doubter’s belief that smoke is produced). Now doubt (against this hypothetical reasoning): Could the smoke come to be from something that is not fire? Or just in some instances could it come to be without fire? Or could it come to be simply by chance (ahetuka, “without a cause”)?