The Commens Dictionary
Quote from ‘Logic of the Sciences’
… if the ground determines the subject in itself, there will be no relation of the representation to its object in itself but only in the subject. No quality of the object will be implied by the representation, therefore, since that would be a ground of agreement in the object. The representation will therefore be unsusceptible of truth. An imperfect example of such a representation is a proper name the ground of which is a convention between the persons who use it. Such a representation may be called an index.
‘Index’ (pub. 04.05.13-16:25). Quote in M. Bergman & S. Paavola (Eds.), The Commens Dictionary: Peirce's Terms in His Own Words. New Edition. Retrieved from http://www.commens.org/dictionary/entry/quote-logic-sciences.