What does Putnam mean by "indexicality"?

Question

I just studied Putnams "Meaning and Reference" (http://home.sandiego.edu/~baber/analytic/Putnam1973.pdf)

Then he talks about indexicality . What exactly does it mean when we say that a word, or some kind of expression is 'indexical'?

Putnam wrote:

"In this paper, our interest is in theory of meaning, however, and not in theory of necessary truth. Words like 'now', 'this', 'here' have long been recognized to be indexical, or token-reflexive -i.e., to have an extension which varies from context to context or token to token. For these words, no one has ever suggested the traditional theory that "intension determines extension."

Can somebody clarify this?

Answer 1

Take for an example the following two sentences:

1. At 12.03.2013 at 12 o clock Lukas was standing on the Golden Gate Bridge.

2. Yesterday I was standing at the Golden Gate Bridge.

In sentence 1 it is clear about which day and which time we are speaking. It is also clear who is standing and where he stands.

In sentence 2 the meaning (and truth) depends upon various things: The speaker, since "I" refers to whoever utters the sentence. The date, because "Yesterday" refers to the day before today. In some cases it might be true, but in some cases it will probably be wrong (except for the case of the utterer standing there everyday).

Terms like "Yesterday", "I", "there", "here" etc. are called indexical, because they can refer to different things.

Answer 2

Indexicals are a certain type of lexical item. They are bits of language that take some information from the context of utterance to determine the meaning of the utterance. For instance, "here" brings in information about the location you are in and might be described as "the location you currently occupy", "now" brings in information about time (e.g., "the time you currently occupy").

You can read more about indexicals and their philosophical interest at this SEP article.