- First, for Peirce the world of appearances, which he calls "the phaneron," is a world consisting entirely of signs. Signs are qualities, relations, features, items, events, states, regularities, habits, laws, and so on that have meanings, significances, or interpretations.
- Second, a sign is one term in a threesome of terms that are indissolubly connected with each other by a crucial triadic relation that Peirce calls "the sign relation." The sign itself (also called the representamen) is the term in the sign relation that is ordinarily said to represent or mean something. The other two terms in this relation are called the object and the interpretant. The object is what would ordinarily would be said to be the "thing" meant or signified or represented by the sign, what the sign is a sign of. The interpretant of a sign is said by Peirce to be that to which the sign represents the object. What exactly Peirce means by the interpretant is difficult to pin down. It is something like a mind, a mental act, a mental state, or a feature or quality of mind; at all events the interpretant is something ineliminably mental.
- Third, the interpretant of a sign, by virtue of the very definition Peirce gives of the sign-relation, must itself be a sign, and a sign moreover of the very same object that is (or: was) represented by the (original) sign. In effect, then, the interpretant is a second signifier of the object, only one that now has an overtly mental status. But, merely in being a sign of the original object, this second sign must itself have (Peirce uses the word "determine") an interpretant, which then in turn is a new, third sign of the object, and again is one with an overtly mental status. And so on.
Thus, if there is any sign at all of any object, then there is an infinite sequence of signs of that same object. So, everything in the phaneron, because it is a sign, begins an infinite sequence of mental interpretants of an object. plato.stanford.edu