The concept has the character of _expressivity;_ that is to say, it is a cognitive product, and, therefore, expressed or spoken, not a mute act of the spirit, as is a practical act. If we wish to submit the effective possession of a concept to a first test, we can employ the experiment which was advised on a previous occasion:--whoever asserts that he possesses a concept, should be invited to expound it in words, and with other means of expression (graphic symbols and the like). If he refuse to do so, and say that his concept is so profound that words cannot avail to render it, we can be sure, either that he is under the illusion of possessing a concept, when he possesses only turbid fancies and morsels of ideas; or that he has a presentiment of the profound concept, that it is in process of formation, and will be, but is not yet, possessed. Each of us knows that when he finds himself in the meditative depth of the internal battle, of that true _agony_ (because it is the death of one life and the birth of another), which is the discovery of a concept, he can certainly talk of the state of his soul, of his hopes and fears, of the rays that enlighten and of the shadows that invade him; but he cannot yet communicate his concept, which is not as yet, because it is not yet expressible. [Sidenote: _Universality._] If this character of expressivity be common to the concept and to the representation, its _universality_ is peculiar to the concept; that is to say, its transcendence in relation to the single representations, so that no single representation and no number of them can be equivalent to the concept. There is no middle term between the individual and the universal: either there is the single or there is the whole, into which that single enters with all the singles. A concept which has been proved not universal, is, by that very fact, confuted as a concept. Our philosophical confutations do not proceed otherwise. Sociology, for instance, asserts the concept of _Society,_ as a rigorous concept and principle of science; and the criticism of Sociology proves that the concept of society is not universal, but individual, and is related to the groupings of certain beings which representation has placed before the sociologist, and which he has arbitrarily isolated from other complexes of beings that representation also placed or could place before him. The theory of tragedy postulates the concept of the _tragic,_ and from it deduces certain necessary essentials of tragedy; and the criticism of literary classes demonstrates that the tragic is not a concept, but a roughly defined group of artistic representations, which have certain external likenesses in common; and, therefore, that it cannot serve as foundation for any theory. On the other hand, to establish a universality, which at first was wanting, is the glory of truly scientific thought; hence we give the name of discoverers to those who bring to light connections of representations