The second department of science is the one which covers the investigation of living organisms. In this field there is such a multiplicity of interrelationships and causalities that not only does the solution of each question give rise to a host of other questions, but each separate problem can in most cases only be solved piecemeal, through a series of investigations which often require centuries; and besides, the need for a systematic presentation of interconnections makes it necessary again and again to surround the final and ultimate truths with a luxuriant growth of hypotheses. What a long series of intermediaries from Galen to Malpighi was necessary for correctly establishing such a simple matter as the circulation of the blood in mammals, how slight is our knowledge of the origin of blood corpuscles, and how numerous are the missing links even today, for example, to be able to bring the symptoms of a disease into some rational relationship with its cause! And often enough discoveries, such as that of the cell, are made which compel us to revise completely all formerly established final and ultimate truths in the realm of biology, and to put whole piles of them on the scrap-heap once and for all. Anyone who wants to establish really genuine and immutable truths here will therefore have to be content with such platitudes as: all men are mortal, all female mammals have lacteal glands, and the like; he will not even be able to assert that the higher animals digest with their stomachs and intestines and not with their heads, for the nervous activity, which is centralised in the head, is indispensable to digestion.
But eternal truths are in an even worse plight in the third, the historical, group of sciences, which study in their historical sequence and in their present resultant state the conditions of human life, social relationships, forms of law and government, with their ideal superstructure in the shape of philosophy, religion, art, etc. In organic nature we are at least dealing with a succession of processes which, so far as our immediate observation is concerned, recur with fair regularity within very wide limits.
Organic species have on the whole remained unchanged since the time of Aristotle. In social history, however, the repetition of conditions is the exception and not the rule, once we pass beyond the primitive state of man, the so-called Stone Age; and when such repetitions occur, they never arise under exactly similar circumstances. Such, for example, is the existence of an original common ownership of the land among all civilised peoples, or the way it was dissolved. In the sphere of human history our knowledge is therefore even more backward than in the realm of biology.
Furthermore, when by way of exception the inner connection between the social and political forms of existence in any epoch comes to be known, this as a rule occurs only when these forms have already by half outlived themselves and are nearing extinction. Therefore, knowledge is here essentially relative, inasmuch as it is limited to the investigation of interconnections and consequences of certain social and state forms which exist only in a particular epoch and among particular peoples and are by their very nature transitory. Anyone therefore who here sets out to hunt down final and ultimate truths, genuine, absolutely immutable truths, will bring home but little, apart from platitudes and commonplaces of the sorriest kind -- for example, that, generally speaking, men cannot live except by labour; that up to the present they for the most part have been divided into rulers and ruled;that Napoleon died on May 5, 1821, and so on.
Now it is a remarkable thing that it is precisely in this sphere that we most frequently encounter truths which claim to be eternal, final and ultimate and all the rest of it. That twice two makes four, that birds have beaks, and similar statements, are proclaimed as eternal truths only by those who aim at deducing, from the existence of eternal truths in general, the conclusion that there are also eternal truths in the sphere of human history -- eternal morality, eternal justice, and so on -- which claim a validity and scope similar to those of the insights and applications of mathematics. And then we can confidently rely on this same friend of humanity taking the first opportunity to assure us that all previous fabricators of eternal truths have been to a greater or lesser extent asses and charlatans, that they all fell into error and made mistakes; but that their error and their fallibility are in accordance with nature's laws, and prove the existence of truth and accuracy precisely in his case;and that he, the prophet who has now arisen, has in his bag, all ready-made, final and ultimate truth, eternal morality and eternal justice. This has all happened so many hundreds and thousands of times that we can only feel astonished that there should still be people credulous enough to believe this, not of others, oh no! but of themselves. Nevertheless we have here before us at least one more such prophet, who also, quite in the accustomed way, flies into highly moral indignation when other people deny that any individual whatsoever is in a position to deliver the final and ultimate truth. Such a denial, or indeed mere doubt of it, is weakness, hopeless confusion, nothingness, mordant scepticism, worse than pure nihilism, utter chaos and other such pleasantries. As with all prophets, instead of critical and scientific examination and judgment one encounters moral condemnation out of hand.
