$44 SLUDIES FOR STUDENTS 
joined in the production of the phenomena. Honors must often 
be divided between hypotheses. One of the superiorities of 
multiple hypotheses as a working mode lies just here. In fol- 
lowing a single hypothesis the mind is biased by the presump- 
tions of its method toward a single explanatory conception. 
But an adequate explanation often involves the codrdination of 
several causes. This is especially true when the research deals 
with aclass of complicated phenomena naturally associated, but 
not necessarily of the same origin and nature, as for example 
the Basement Complex or the Pleistocene drift. Several agen- 
cies may participate not only but their proportions and impor- 
tance may vary from instance to instance in thesame field. The 
true explanation is therefore necessarily complex, and the ele- 
ments of the complex are constantly varying. Such distributive 
explanations of phenomena are especially contemplated and 
encouraged by the method of multiple hypotheses and consti- 
tute one of its chief merits. For many reasons we are prone to 
refer phenomena to a single cause. It naturally follows that 
when we find an effective agency present, we are predisposed to 
be satisfied therewith. We are thus easily led to stop short of 
full results, sometimes short of the chief factors. The factor 
we find may not even be the dominant one, much less the full 
complement of agencies engaged in the accomplishment of the 
total phenomena under inquiry. The mooted question of the 
origin of the Great Lake basins may serve as an illustration. 
Several hypotheses have been urged by as many different stu- 
dents of the problem as the cause of these great excavations. 
All of these have been pressed with great force and with an 
admirable array of facts. Up to a certain point we are com- 
pelled to go with each advocate. It is practically demonstrable 
that these basins were river valleys antecedent to the glacial 
incursion. It is equally demonstrable that there was a blocking 
up of outlets. We must conclude then that the present basins 
owe their origin in part to the preéxistence of river valleys and 
to the blocking up of their outlets by drift. That there is a 
temptation to rest here, the history of the question shows. But 
