watch house omcers dealing with diagnostic problems in the casualty department (Richards et alii, 1968). It was quite clear that they structured their activities in history, examination and investigation of the patients almost from the outset in a heuristic manner, seeking always for a diagnostic goal which, though only dimly perceived, gradually became clearer. Their activities, in fact, traced a network of data out of an available field, rather than exploring the field at random or systematicallY. Heuristic thinking is both a powerful and a dangerous tool: powerful, because it has similarities with other scientific methodologies which are at present exciting a good deal of interest; dangerous, because as with pattern recognition we may wrongly identify our goals and so reach a conclusion not in accord with the patient's interests, even though it may satisfy ours. I should finallY draw your attention to a variant of heuristic thinking that must often be dominant in the mind of the surgeon who is called upon to act when information Is Incomplete. This brings us Into fleeting contact with a further area of logical thought-games theory-which has become of Importance in other fields of human activity (Neuman and Morgenstern, 1947). The surgeon faced with the problem of the acute abdominal emergency must weigh not only the probability of one or other diagnosis In terms of a-priori likelihood, but also must consider the outcome for his patient of makIng a particular diagnosis. In specific terms, If. he decides not to operate on a patient who presents with signs compatible with an acute abdominal emergency because he feels that the patient does not have a condition which will be helped by operation, he must, before he makes up his mind, weigh the effect of this decision on his patient if, In fact, the chosen diagnosis is wrong. We are, In such Instances, trying to assess what Is known as "pay-off" for the patient consequent upon choosing a particular diagnostic and consequently therapeutic strategy. When It can be foreseen that the pay-off Is against the patient as a result of choosing what appears to be the likely diagnosis should that diagnosis In fact be wrong, then it must on occasion be necessary to proceed "as if" a less likely diagnosis is present. In the acute abdominal emergency, in which matters are rapidly progressive, this is a not uncommon situation, and the more we look at ourselves engaged In the diagnostic process, the more we realize that we are often dealing in terms of pay-off in our management of Individuals. The same can, of course, be true In constructing more leisurely diagnostic or therapeutic strategies. What I hope that I have done Is to demonstrate to you that not only Is there a great deal of complexity In the diagnostic process which we use every day, but also that our approach to it on an empirical or artistic basis Is no longer satisfactory. There Is gradually coming together information which would allow us to make some rational statements about what we do and thus to transform some of the mystique of what we teach into Intelligible and rapIdly learnt sequences. In this manner, we may strengthen the diagnostle hand of the next generation of doctors, whether that hand palpates the abdomen or types on a computer console.
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