But however preponderating the part claimed by this cause in acts exclusively human may be, it has nothing to do with those phenomena which have their origin in the intelligence alone. The learned mathematician who seeks by the aid of the most profound abstractions the solution of some great problem, is completely without the moral or religious sphere into which, on the contrary, the ignorant, simple-minded man enters when he struggles, suffers, or dies for justice or for his faith. IX. It was necessary to recall all the facts and theories which I have just summed up, in order to facilitate the comprehension and the justification of the method which alone can guide us in anthropological studies. The object of anthropology is the study of man _as a species_. It abandons the _material individual_ to physiology and medicine; the _intellectual_ and _moral individual_ to philosophy and theology. It has, therefore, its own special field of study, and on that account alone its special questions, which often could not be solved by processes borrowed from cognate sciences. In fact, in some questions, and in some of the most fundamental ones, the difficulty lies in the interpretation of phenomena connected with those which are characteristic of all living beings. For the very reason that they are to a certain extent obscure in man, we cannot seek for an explanation of them in man, since he becomes, so to speak, the unknown quantity of the problem. An endeavour to solve the problem by the study of man, who is the object of it, would be equivalent to a mathematician representing the value of _x_ in terms of _x_ itself. How does the mathematician proceed? He seeks in the data of the problem for a certain number of _known quantities_ equivalent to the _unknown quantity_, and by means of these quantities he determines the value of _x_. The anthropologist must act in the same manner. But where must he seek for the known quantities which will enable him to state the equation? The answer to this question will be found in what we have said above, and in the table of kingdoms. Man, although he has his special and exclusively human phenomena, is above all an organised and living being. From this point of view he is the seat of phenomena common to animals and plants; he is subjected to the same laws. In his physical organisation he is nothing more than an animal, somewhat superior in certain respects to the most highly developed species, but inferior in others. From this point of view he presents organic and physiological phenomena identical with those of animals in general, and of mammalia in particular; and the laws which govern these phenomena are the same in both cases.