But even in the midst of this actual world there is present an inconsistent element, a human race with a confused logic. This race has been led by various depressing and saddening circumstances to blacken the delicious truth of this world and to look for a transcendental truth in philosophical metaphysics or religious fantasmagorias, both of which are parts of the same stew. The philosophers of misery who make of the world of truth a vain shadow and a miserable vale of sorrow must needs be convinced by logic that the living world is the only true one. Well, that is not so difficult. But there is a danger of getting into a vicious circle of errors, imitating a snake biting its own tail. I have to prove logically that the world and truth are one and the same thing, before we have come to an agreement as to what is logical truth or true logic. Nevertheless, nature has assisted us. The logic of nature is the true logic by the help of which we can agree. Nothing more is required than a somewhat trained brain. Take two men having a dispute about truth. One of them says it is one thing, the other that it is something else. So they are arguing about that which is. This last word is a form of the verb to be. Hence in arguing whether the remote nebula in the heavens is a brick or a star, a male or a female, one is always discussing some form of existence. All disputes turn around forms of existence, but existence itself is an undisputable truth. Have I now still to prove that all existence is of the same category? Are there any stones that do not belong to the category of stones, or any kind of wood which is iron? What would become of reason and language, if such a thing were to be considered? And yet, much that is being said by opponents is of such a nature. If I have succeeded in convincing you that the universe is the truth, there still remains the special question: What place shall we assign to fantastic ideas, error, and untruth? If the universe is the truth, then everything would be true, and hence it seems contradictory that error and untruth should have a place in truth or in the world. Of this more anon. I shall only point out in passing that untruth may without any contradiction belong to truth, just as weeds are a negation of herbs and still at the same time herbs. In conclusion I call your attention to the eminently proletarian character of the science of truth. It gives to the working class the logical justification to renounce all clerical and mystic control and to look for salvation in this same world in which divine truth is living. SEVENTH LETTER The philologists distinguish carefully between a science of language and a science of languages. The latter teaches Egyptian, Assyrian, Hebrew, Greek, Latin, English, French, etc., while the former treats of the general characteristics common to all languages, of language itself.