(1) Its distinguishing trait is that it defines thought or intelligence by function, by work done, by consequences effected. It does not start with a power, an entity or substance or activity which is ready-made thought or reason and which as such constitutes the world. Thought, intelligence, is to it just a name for the events and acts which make up the processes of analytic inspection and projected invention and testing which have been described. These events, these acts, are wholly natural; they are "realistic"; they comprise the sticks and stones, the bread and butter, the trees and horses, the eyes and ears, the lovers and haters, the sighs and delights of ordinary experience. Thinking is what some of the actual existences _do_. _They_ are in no sense constituted by thinking; on the contrary, the problems of thought are set by _their_ difficulties and its resources are furnished by _their_ efficacies; its acts are _their_ doings adapted to a distinctive end. (2) The reorganization, the modification, effected by thinking is, by this hypothesis, a physical one. Thinking ends in experiment and experiment is an _actual_ alteration of a physically antecedent situation in those details or respects which called for thought in order to do away with some evil. To suffer a disease and to try to do something for it is a primal experience; to look into the disease, to try and find out just what makes it a disease, to invent--or hypothecate--remedies is a reflective experience; to try the suggested remedy and see whether the disease is helped is the act which transforms the data and the intended remedy into _knowledge objects_. And this transformation into knowledge objects is also effected by changing physical things by physical means.