It is relative in the first place to our organisation. Here Comte takes up again an idea which was dear to the philosophers of the XVIII. century and in particular to Diderot. If our organisation were different, the data which our science elaborates would be other that they are. With more organs we might perhaps grasp kinds of problems of which we have no idea. If we suppose our species to be blind, astronomy would not exist for it. And further, a natural law requires that the more complex and the higher phenomena in regard to their conditions of existence, should be subordinated to the more general and the more common phenomena. The intellectual phenomena thus depend, first, upon the biological phenomena, and then upon all those to which the biological phenomena are subordinated. In this sense, therefore, science is relative to our organisation, which is itself relative in respect to the milieu in which we live. But, reciprocally, the representation of this milieu and of this organisation rests upon intellectual laws which impart to science a need of unity and harmony special to the mind. Comte concludes, therefore, that to endeavour to apportion what belongs to the object and what to the subject in scientific knowledge is a hopeless attempt. We simply know that science is not the exclusive product either of the subject or the object. Giving too much to the object leads us to “empiricism.” Falling to the opposite extreme leads to “mysticism.” The efforts of philosophers to construct an abstract theory of knowledge have only ended in miserable results. We have not gone beyond Aristotle’s “axiom as corrected by Leibnitz.” _Nihil est in intellectu quod non prius fuerit in sensu, nisi ipse intellectus._ We are only certain of one thing: our science, necessarily conditioned by our organisation, is also necessarily relative. But this is not the most decisive consideration for it only makes us see that our science would be different, if our organisation were to change. Now, as a matter of fact, our organisation does not change. Human nature, according to Comte, remains similar to itself in the whole course of its evolution. It is this evolution which itself becomes a cause, and a decisive one, of relativity for science. For, if our organisation does not vary, the system of our conceptions and of our science necessarily varies, according to our “situation,” that is to say, according to the position which we occupy in this evolution, which accomplishes itself according to laws.