METHODS OF THE EARTH-SCIENCES. 73 



dicated. If the earth as a whole is as rigid as steel, and the outer part 

 is, as we know, formed of rock much less rigid than steel, the interior 

 must be much more rigid than steel and there must be a differential 

 distribution of rigidity. The new inquiry may then well start with the 

 assumption of increasing rigidity toward the center. Postulating an 

 earth so constituted, a first step of the regenerated inquiry might well 

 be an effort to learn not only the amount of the tidal protuberance, but 

 also the position of the protuberance, since its position is as essential 

 as its amount in influencing the motions of the earth and moon. As 

 a geologist I venture f o entertain the belief that exhaustive inquiry on 

 such regenerative lines would bring forth results in harmony with 

 geological evidences, with which the well-known conclusions heretofore 

 reached seem to be at fatal variance. 



The earth-sciences are not purely physical sciences. They con- 

 cern themselves with life and with mentality, as well as with rocks, 

 ocean and atmosphere. Our group is exceptionally comprehensive in 

 the range of its subjects. Our methods should hence be such as to 

 encompass the whole field. They should give us ultimately a com- 

 plete working system of thought relative to all the earth is or holds. 

 In some sense the earth sciences must come to comprehend the essentials 

 of all the sciences. At least as much as any other scientists we are in- 

 terested in the fundamental assumptions of all the sciences and in 

 their consistent application. To touch hastily this broader field, I 

 choose a second illustration of the method of regenerative hypotheses 

 from the relations between the assumptions of science and the con- 

 clusions of science. 



As our working basis, we assume that our perceptions represent 

 reality, when duly directed and corrected, but that error and illusion 

 lurk on all sides and must be scrupulously avoided. We assume that 

 we are capable of detecting error and of demonstrating truth ; and that, 

 as requisite means, we have choice, and some measure of volitional com- 

 mand over ourselves and over nature. 



Starting thus with assumptions that embrace choice and the pos- 

 sibility of error, and going out into physical research, most of us have 

 concluded that antecedents are followed rigorously by their consequents. 

 Going out a step further into the chemico-biological field and noting 

 the close interrelations between physical and vital phenomena, many 

 of us have been led to a belief in their ultimate identity. Going out 

 a step further into the mental field, not a few of us have concluded 

 that an unvarying sequence of antecedents and consequents reigns here 

 also. But this seems to contradict the assumptions with which we 

 started. Our primary assumptions embraced choice, volitional control, 

 and the alternative of reaching truth or falling into error according to 

 our self-directed discrimination. 



What is to be done in the face of this seeming contradiction? The 

 method of regenerative hypotheses answers that a new set of assump- 



