A deictic expression depends on the context of use, like saying "left" rather than "north" (that's a more-or-less thing). This is the most powerful word we have--it lets us express without naming, so long as we have a similar conception of what kind of things can be pointed at. (For example, we can discuss unseen landmarks because humans have a common understanding of what sort of features can be considered landmarks. This is informed by a landmark-recogniser in the brain and the world itself.) It's relative linking. But as it good as it is, we need absolute addresses too (see yesterday for an address typology). It's better still if we can switch between them:
Deictic signs are often useful--"you are here," "next bus in 10 minutes," "campground 200 yards ahead on the right"--but so too are less indexical representations ("4421 Hingston Avenue; 5.13 A.M. Wednesday, November 29, 1950"). That way lies external (derivative) representation, documents, and writing. Skill in using and creating signs involves appropriate combination. In particular, the problem with deictic signs in that the original difficult recurs: as soon as you drive off and become separated from the sign, it can no longer be immediate [...] As a result, complex cascades of registration, more and less deictic, are often useful, and sometimes essential. Thus you remember where the map is; the map "remembers" the directions to the lake. Or, more fully: you remember where the map is; the map "remembers" the directions to the road that runs by the lake; once there, effectively accessible (encounterable) road signs indicate the turnoff for the campground; at the campground addition (deictic) signs indicate exactly where to pitch your tent. And so on and so forth. -- Brian Cantwell Smith, On the Origin of Objects, p236.