 Notice that if this description is to succeed in determining the appropriate broad content on Earth and on Twin Earth, then it must have a subtle “indexical” component. An indexical is a term, like ‘I’ or ‘now’, whose referent is context-relative. The referent of ‘I’ depends on who utters or thinks it; the referent of ‘now’ depends on the time at which it is uttered or thought. The supposedly narrow content “colorless odorless liquid that falls from the sky and fills the lakes” must have an implicit indexical component: the content in question is really something like “the colorless, odorless liquid that falls from the sky and fills the lakes around here” (Putnam 1975, p. 234).