The Commens Dictionary
Quote from ‘Logical Tracts. No. 1. On Existential Graphs’
An informant index is a proposition. For one cannot better define a proposition (as distinguished from the assertion whereby one assumes responsibility for its truth) than as a representation of which one part serves, directly or indirectly, as an index of its object, while the other part excites in the mind an image of the same object.
MS [R] 491:5
‘Informational Index’ (pub. 08.08.17-12:05). 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-logical-tracts-no-1-existential-graphs-15.