The demonstration of this law presents itself under two distinct forms. In the first place Comte supports his argument by history. This proves indeed that every branch of our knowledge passes in turn through the three states, with never a single retrogression. It is true that much of our knowledge has not yet reached the positive state. But at any rate it is established that up to the present even those sciences which have not yet reached that state have all described the same curve, already described by those that have reached it. Historical verification would suffice, if necessary, provided it were complete. Comte is not satisfied with it. He claims moreover to deduce the law of the three states from the nature of man. He will thus give a direct demonstration of it. However useful history may appear to him as an instrument of proof, he still wishes to render its verdict intelligible. To reach this end he has recourse to psychology. “We ought,” he says, “carefully to characterise the general motives, drawn from an exact knowledge of human nature, which must have rendered partly inevitable, partly indispensable, the necessary succession of social phenomena, considered directly with respect to the intellectual development which dominates essentially their chief advance.”[15] In the first place, the human mind could only begin to interpret nature by a philosophy of the theological type. For it is the only one which is spontaneously produced, the only one which does not presuppose another. Man at first conceives all activity on the same plan as his own. In order to understand phenomena, he likens them to his own actions, whose mode of production he thinks he apprehends, because he has the feelings of his own efforts and the consciousness of his own volitions. This anthropomorphic explanation comes so naturally to us that we are always ready to give way to it. Even to-day, if we forget positive discipline for a moment, if we venture to ask for the mode of production of some phenomenon, we immediately dimly imagine an activity more or less like our own. And among the metaphysicians who profess to give an idea of God, the most consistent, according to Comte, are those who make a person of Him.