66 



SCIENCE 



[N. S. Vol. XXXVI. No. 916 



before, but I venture to predict that if you 

 live and succeed, you will do it many times 



The Greek philosopher Heraclitus laid 

 weight on the idea that all things are in a 

 state of flux. The notion has not always 

 been approved. We know that this idea in 

 some of its aspects was repugnant to the 

 early Victorian gentlemen, but to-day we 

 are less prone than those of earlier genera- 

 tions to dogmatize on the impossible, and in 

 this country and this phase of civilization, 

 we feel with its full force the forward flow 

 of things, so that for us nothing is more 

 certain than the progressive change and 

 onward movement in medical theory and 

 hence in medical practise. 



During the years of your training you 

 have been carried more or less uncon- 

 sciously along and thus helped to keep in 

 touch with the development of medical 

 thought, but at this moment, when the 

 stream of knowledge is about to cast you 

 out upon its shores and you are asked to 

 walk on alone, it is worth while to inquire 

 what is your preparation for the experience. 



From these halls and laboratories you 

 bear away a load of learning — haply you 

 bear it lightly. It is to this possession that 

 I wish to direct attention for a moment. 



The knowledge we accumulate is a very 

 mixed article, but in this mixture there are 

 two sorts which it is well for us to consider 

 now. One sort consists of certain formulas 

 which control our incidental actions; for 

 instance, we all know on occasion when to 

 stand up or to sit down, and you know the 

 technique and procedure for various sur- 

 gical operations. A great fraction of our 

 information is in this form, a form not 

 necessarily subject to frequent or radical 

 change. This sort, however, is of minor 

 interest to us now, and has been mentioned 

 here only that it may serve as a foil to the 

 more important kind. 



This more important kind of knowledge 

 is that on the basis of which we can foresee 

 and predict. 



There are manifold varieties of this and 

 they range from that which permits us to 

 predict with a high degree of confidence 

 the rising of to-morrow's sun, to that with 

 which one ventures to predict the weather 

 or the fate of a patient with baffling sjonp- 

 toms. 



In these latter instances the course of 

 events is by no means unpredictable, but 

 only so dependent on complex factors and 

 conditions that we rarely have at once at 

 hand enough information to make a re- 

 spectable guess. This fact bears very di- 

 rectly on the matter before us, for when we 

 scrutinize our intellectual possessions we 

 find them to consist in large measure of 

 information useful for prediction, yet 

 mainly information so incomplete that the 

 conclusions or theories — if you choose — 

 based on it must be largely held as open to 

 revision and therefore can be used with 

 safety only by those who carry in mind 

 just how much or how little each conclu- 

 sion has to rest upon. Nevertheless, it is 

 just these tentative conclusions or theories 

 which the medical man must so largely 

 utilize. Probably you have thought of this 

 before ; if so, you know that to the revela- 

 tions of this analysis men react in very 

 different ways. Some throw up their hands 

 in the face of so much uncertainty; others 

 stretch certainty to the limit and seek to 

 make it cover all they have been taught 

 and then cultivate impenetrability because 

 change is disquieting and new knowledge 

 means new labor, while those born under 

 happier stars are neither crushed nor 

 blinded, but recognize that intellectual 

 health and vigor imply an unceasing re- 

 placement of both data and conclusions, to 

 be accomplished only when the period of 



