490 SCIENCES OF THE EARTH 



followed for the most part inductive or even only empirical methods, 

 as has so generally been the case with geography. 



For example: in the study of the tides already referred to, how 

 unanimous we are as to the inadequacy of inductive methods; how 

 universally we accept the marvelous theoretical scheme of inter- 

 action between planet and satellite, deduced from tidal theory; how 

 we admire its extension to the supposed relation of the inferior 

 planets to the sun. But in general geography, how little attention 

 has been given to the deductive and systematic consideration of 

 its many problems: how many geographers still look rather askance 

 at those of their number who propose to treat geographical problems 

 through theory as well as through observation! It seems to me 

 clear that, while the earlier progress of geography was very largely 

 inductive, the later progress has been largely determined by a free 

 acceptance of deductive as well as inductive methods, and that 

 geography as well as geology is to-day profiting greatly from the 

 use of our faculty of insight as well as of outsight. 



The objections that are not infrequently urged against the employ- 

 ment of indirect, inferential, as well as of direct, observational 

 methods in certain branches of our science come from two sides. On 

 one side is a misapprehension as to the nature of our tasks, a belief 

 that our work may really be largely inductive, that observation 

 alone will suffice, if patiently continued, to discover all pertinent 

 facts. This is a serious mistake: there is everywhere more unseen 

 than seen. On the other side is the fear that theories may become 

 our masters and that we may appeal to them as infallible, and 

 thus set ourselves up as authorities. This is a most natural induc- 

 tion from the history of our earlier progress, for we have repeat- 

 edly seen the sincere young investigator grow into the impatient 

 old autocrat: it is a bit of human nature that we share with the 

 rest of the world; it is analogous to the change of meaning in the 

 word tyrant, from a mere king to an arbitrary despot. But there is 

 another verbal analogy in the change of the word skeptic, from in- 

 quirer to doubter, and it is this analogy that we are now following. 

 We have learned to doubt because we know we may be deceived; 

 we mistrust careless eyes as well as careless thoughts, and insist 

 that careful scrutiny be given to the work of each: we reduce the 

 dangers of theorizing, just as we reduce the errors of observing, 

 not by avoiding that indispensable means of investigation, but by 

 practicing it carefully, until we become experts in thinking as well 

 as in seeing; and all this constitutes an important element in our 

 recent progress. 



In spite of what has already been gained by good theorizing, few 

 realize how largely earth-science, apparently a matter of observa- 

 tion, is really built up of inferences that go far beyond mere indue- 



