Sheila: Health experts generally agree that smoking a tobacco product for many years is very likely to be harmful to the smoker' s health. Tim: On the contrary, smoking has no effect on health at all: although my grandfather smoked three cigars a day from the age of fourteen, he died at age ninety-six. A major weakness of Tim's counterargument is that his counterargument ['tacitly assumes that those health experts who are in agreement on this issue arrived at that agreement independently of one another', 'presupposes that longevity and health status are unrelated to each other in the general population', 'attempts to refute a probabilistic conclusion by claiming the existence of a single counterexample', "describes an individual case that is explicitly discounted as an exception to the experts' conclusion"]