INVESTIGATION VERSUS PROPAGANDISM 333 



its eminent fairness, requires us to make an earnest effort to bring 

 under trial all tenable alternatives, to the end that among these 

 there may be found the one that apportions the task of revision 

 in strict accord with the inherent value of the combined evidence. 

 This in its very nature also covers the question whether or not it 

 is possible to escape all serious revision of criteria by finding some 

 tenable basis of reconciliation not perhaps now recognized. 



How such a series of multiple working hypotheses is to be built 

 up from the one we have just suggested is almost obvious, for the 

 one just offered is a rather extreme one and quite suitable to form 

 the end hypothesis nearest us in time. To build out the series 

 from this backward in time, it is merely necessary to push back 

 step by step the assigned place in time of the basal creek deposit 

 and note the degree of strain put on each of the several criteria 

 of interpretation by each step. The measure of total strain in 

 each case — or the best balance of such strain as is unavoidable- 

 forms the index of success of each trial hypothesis. 



In studying such a series it will be not only interesting but 

 significant to note that, if we accept the interpretation of the creek 

 deposits already sketched, the extinct vertebrates may be assigned 

 earlier and earlier ages without necessarily bringing any strain at 

 all to bear upon the archaeological and anthropological evidences, 

 for the human relics were buried at horizons so close under the 

 deposits in process of formation when suspended in 19 13 that any 

 tenable amount of backward assignment of the content of the 

 lower layers is not likely to carry these relics back beyond the 

 place their own criteria would assign them on independent 

 grounds. The strains that are really brought out by such back- 

 ward steps in assignments of the date of deposition of the extinct 

 vertebrates or of the plants bear almost solely on the criteria 

 derived from physico-dynamic and regional considerations. The 

 question of the Pleistocene or the non-Pleistocene age of man is 

 thus replaced by the much broader and deeper question, What are 

 the relative worths of the criteria off'ered by life-extinctions on the 

 one hand, and those offered by physical state, dynamic work 

 done, regional distribution and stratigraphic arrangement, on the 

 other ? 



