THE DISCIPLINARY VALUE OF GEOGRAPHY 113 



he shall gain a full explanation of all the observed facts; that is, an 

 understanding of the manner in which they have been produced. While 

 the invented counterpart remains of uncertain value, because untested, 

 it is often called an hypothesis; and its uncertainty may be further 

 indicated by calling it a provisional, or a working hypothesis. If later 

 on, it survives all the tests that can be applied to it, it is then usually 

 called a theory; or in order to emphasize its proved value, an estab- 

 lished theory. But it is never, so far as the unseen facts of the past 

 are concerned, anything more than the mental counterpart of those 

 facts. Indeed, inasmuch as an hypothesis, when first invented, is 

 usually based on only a few of the observed facts, it will then be only 

 the counterpart of a few of the facts of the past, or of some general 

 principle that suggests the genetic relation of partial groups of facts, 

 past and present. Much more than the mere invention of such an 

 hypothesis must be done before a complete explanation of all the facts 

 is reached; and it is through the additional work, by which supple- 

 mentary facts and fancies are correlated, that an invented hypothesis ia 

 tested. 



As soon as the tentative nature of an hypothesis is understood and 

 its possible failure is recognized, the investigator should realize that he 

 must not stop inventing when his first hypothesis is brought forth; he 

 must urge his subconscious mind to continue bringing forth inventions 

 as actively and ingeniously as possible. He must thus equip himself 

 with several rival working hypotheses,^ to each of which he must give 

 warm welcome and impartial friendship, but to none of which must he 

 offer special protection or advocacy. The defence for a hypothesis is 

 provided chiefly from new details that are added to it after its inven- 

 tion, or by new facts which are brought to light by its aid. If no 

 defense of this kind is found, the hypothesis must be regarded as only 

 a tentative speculation. 



Deduction of the Consequences of an Hypothesis. — Before any 

 decision as to the truth of a hypothesis is attempted, the question 

 must be asked: What consequences must it have in addition to those 

 facts which it was made to explain ? An altogether new faculty is now 

 called into play, the faculty of deduction, by which the consequences 

 of a hypothesis are logically worked out. Here again experimenta- 

 tion is extremely useful in physics and chemistry, and it is coming to 

 be more useful than it has been in biology and geology; but in the 

 study of land forms experiment is at present rather imitative than 

 demonstrative, and it will not be further considered here. What we 

 have to examine now is a logical faculty that can be more consciously 

 used than invention, but one which, unlike observation, can be carried 



* T. C. Chamberlin, " The Method of Multiple Working Hypotheses," Joum. 

 Geol., v., 1897, 837-«48. 



