A careful review of hospital fatalities due to anesthesia during the last 20 years indicates that the most significant safety improvements resulted from better training of anesthetists. Equipment that monitors a patient' s oxygen and carbon dioxide levels was not available in most operating rooms during the period under review. Ttherefore, the increased use of such monitoring equipment in operating rooms will not significantly cut fatalities due to anesthesia. A flaw in the argument is that ['the evidence cited to show that one factor led to a certain result is not sufficient to show that a second factor will not also lead to that result', 'the reason indicated for the claim that one event caused a second more strongly supports the claim that both events were independent effects of a third event', 'the evidence cited to show that a certain factor was absent when a certain result occurred does not show that the absence of that factor caused that result', 'the reasons given in support of the conclusion presuppose the truth of that conclusion']