Bibliography

Logic Chapter I

… comparison is the determination of a representation by the medium of that which is present, in contradistinction to its determination simply by that which is present. For example, I put A into relation to B, when in contemplating A, I as it were see B through it. The representation determined by the medium of A, may be called its correspondent. Then the immediate function of reference to a correlate is to conjoin that which is presented with its correspondent, and the introduction of the former conception is justified by the fact that only by it is the latter made representable. Accordingly reference to a correspondent is the third conception with content.

… the relation of a repraesentamen to its object (correlate) may be a real relation and, then, either an agreement or a difference, or it may be an ideal r[elati]on or one from which the reference to a correspondent (subject of representation) cannot be prescinded by position. [—] In the second case, there is a real difference of the repraesentamen from its object, that is to say not a mere difference in quality but also a bringing of them together in nature; in this case the representative character of the one will consist in constant accompaniment by the other, so that it indicates the existence of the latter without noting any characters of it. Such a representation may be termed an index.

… the relation of a repraesentamen to its object (correlate) may be a real relation and, then, either an agreement or a difference, or it may be an ideal r[elati]on or one from which the reference to a correspondent (subject of representation) cannot be prescinded by position. In the first case, that is where the repraesentamen has a real agreement with its object, the representation consists in a likeness; a simple quality of the object is shown but the object itself is not said to exist.