Thus the definitions, and even the laws, established by the positive sciences, are at every period approximations corresponding to the knowledge we have of facts. And as this knowledge can always be enriched the approximation may also become stricter, without ever reaching its confines. Leibnitz already said that the analysis of anything real reaches to infinity. This thought is with him, closely allied to the whole of his metaphysics. We find in Comte an expression in some way equivalent, although positive. He says, although the progress of the science of nature consists in substituting as much as possible the rational method to the experimental method, the limit can never be attained, we can never affirm that experience will not bring new elements which will oblige us to modify the edifice of science. The relativity of science thus serves to maintain an equal balance between the need of unity which comes from the understanding, and the inexhaustible diversity of the world of reality which this understanding studies.
As a fact, then, positive science is always relative. Rightly, it cannot be otherwise, and this for two essential reasons. It depends necessarily upon “our organisation” and “our situation”[44] or, in other words, it is relative “both to the individual and to the species in its advance.”
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.
Our conceptions, our religions, our philosophies, are not only individual phenomena; they are also and chiefly social phenomena, moments in a collective and continuous life, of which all the phases are interdependent. We only know in a given order of knowledge, what is compatible at that moment with the generally admitted philosophy, with the knowledge already acquired in this and in the other orders of phenomena, with the great hypotheses considered as true, with the methods in force, etc. As soon as the human mind has become conscious of the evolution to which it is subject, as soon as it has grasped its most general law (the law of the three states), in a word, as soon as sociology is founded, science can no longer be conceived as other than relative. For from that moment the various sciences appear as so many great social facts, which vary as so many functions of the rest of civilisation.
Our speculations, “depending on the totality of social progression,” can therefore never admit of that absolute fixity which metaphysicians have supposed. The continuous movement of history modifies, in the long run, the beliefs which appear to be the most immutable. Our theories tend to represent more and more faithfully the objects of our investigations, that is to say the laws of phenomena. We are thus brought back to the idea of limit, which is never attained, towards which we are advancing by means of approximations ever more exact.
The time is not yet far distant, when a doctrine of this kind could not have been advanced without at once being rejected as sceptical. The human mind is scarcely beginning to understand that truth cannot be immutable.[45] Men believed that truth must always be identical with itself, always identical for all minds at all times and at all places. It seems that in losing this character, it must cease to be truth. That is why philosophy has been so persistent in the pursuit of the absolute. It was believed that no truth could be certain, unless it rested, ultimately, upon an immutable foundation.
Science was therefore made to hang on metaphysics. And the defeats, a thousand times repeated, of metaphysics would not have discouraged the human mind had not positive philosophy at last shown that the truth of which we are capable, because it is relative does not cease to be truth. We are not condemned to choose between the pursuit of an inaccessible absolute and the crumbling down of all science. It suffices to understand that human science evolves and that this evolution is subject to laws. It is never ended: it always “becomes.” It is not a “state:” it is a “progress.”
There are therefore provisional, and, if one may so speak, temporary truths. Does science ever establish any others? The ideas which Hipparchus and the Greek astronomers had of the heavens was not false in all respects. It was the astronomical truth compatible with the conditions of the society in which they lived. After the labours of the observers of the Middle Ages, utilised by Copernicus, this idea faded before another one which became more perfect with Newton and Laplace. Perhaps this one will be modified in its turn, in consequence of new discoveries! Similarly it was thought that the earth was a flat surface, then a round disc. Then it was represented as a sphere and finally as an ellipsoid. To-day we know that this ellipsoid is irregular.