(denotations) plus semantic fields of the term chosen for the verbal reference. The term of the dictionary includes connotations and possible denotations which are relevant in the context of the presentation of One and Three Chairs. The meanings of the three elements are congruent in certain semantic fields and incongruent in other semantic fields: A semantic congruity ("One") and a threefold incongruity ("One and Three"). Ironically, One and Three Chairs can be looked upon as simple but rather complex model, of the science of signs. A viewer may ask "what's real here?" and answer that "the definition is real"; Without a definition, one would never know what an actual chair is. There exist different interpretations of these semantic and ontological aspects. Some refer to Plato's Republic (Book X); others refer to Ludwig Wittgenstein´s Tractatus or to Charles Sanders Peirce's triad icon-index-symbol. Dreher discusses the semantic problems of One and Three Chairs as inclusions of circles which represent semantic fields. The work tends to defy formal analysis because one chair can be substituted for another chair, rendering the photograph and the chair photographed elusive to description. Nevertheless, the particular chair and its accompanying photograph lend themselves to formal analysis. There are many chairs in the world; thus only those actually used can be described. Those chairs not used would not be analyzed. The enlarged dictionary definition of the word chair is also open to formal analysis, as is the diagram containing instructions of the work. The concept and the theory of art Kosuth's thematization of semantic congruities and incongruities can be seen as a reflection of the problems which the relations between concept and presentation pose. Kosuth uses the related questions, "how meanings of signs are constituted" and "how signs refer to extra-lingual phenomena" as a fundament to discuss the relation between concept and presentation. Kosuth tries to identify or equate these philosophical problems with the theory of art. Kosuth changes the art practice from hand-made originals to notations with substitutable realizations, and tries to exemplify the relevance of this change for the theory of art. In "Art after Philosophy," Kosuth provoked a confrontation with the formal criticism of Clement Greenberg and Michael Fried. Both exposed the concept of the art work as a non-substitutable instance realized by an artist who follows no other criteria than visual ones. They defined this concept as the core of modernism. In the sixties, Greenberg's