Had the study of the psychical functions been made upon animals at the same time as upon man, this error would not have lasted long. But philosophers were maintained in it, on the contrary, by metaphysical and even theological preoccupations. The science of mental functions had to establish a difference, not only of degree but of kind between man and animals. It was further required, by reason of another necessity closely allied to the former, that the soul should be considered as being immortal. And it was consequently necessary that the “ego” should present metaphysical characteristics of unity, of simplicity and of identity. Now, it is by thought that man is most distinguished from animals. It is therefore from thought that the characteristics attributed to the soul or to the “ego” have been borrowed. But in fact the “ego” is not the absolute unity which the eclectic psychologists say that it is. It represents the feeling which the superior living being has, at every moment of the “sympathies” and the “synergies” which take place within the organism. It is the conscious expression of what the French call to-day “cénesthésie.” Far from being directly perceived as Cousin asserts, it is the indirect product of a quantity of sensations and sentiments, of which the majority are not perceived in the normal state.[185] It is especially by pathological facts, (diseases of the personality, double consciousness, lunacy, etc.), that the attention of the scientific man is drawn to this very complex phenomenon. It is, moreover, impossible to regard the sentiment of the “ego” as belonging exclusively to man. Everything leads us to believe that it also exists in the other higher animals. In any case there is no metaphysical doctrine to be founded upon this exceedingly complex and very unstable sentiment. Comte is here speaking as the successor of Hume and of Cabanis. In the clearest manner he defines his opposition to Cousin’s doctrine. The latter draws the whole of philosophy from the analysis of the “_ego_,” Comte draws nothing from it. He does not, however, stop to show the superiority of the positive method over theological or metaphysical method in this matter. Of what use would it be? The progress of science, in the end, gets the better of methods which have become antiquated and barren. Metaphysicians have already passed from the state of “domination” to that of “protestation.”[186] And when the positive method gets a footing in an order of phenomena, there is no instance in which, sooner or later, it has not asserted its mastery over it. II.