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 to 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 concern 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 complete 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 interested 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 conclusions 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 command over ourselves and over nature.
Starting thus with assumptions that embrace choice and the possibility 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-
