Symbol, from the Greek symbolon, means a broken piece, one half of which signifies the existence of the other, a presence that indicates what is absent. The incompleteness of the presence, but the incompleteness of the absence: symbionts.

Every object is afloat on the processes that created it and will consume it. It can be read as a symbol of those processes and scrutinized for signs of them. What is present should speak of what is absent. Not only words and pictures tell their stories, things do as well in a language older than imagemaking or speaking. That is, the world itself is a language that speaks to us (thus geologists speak of reading rocks, doctors of reading x-rays). Every thing serves as evidence: the feather of the bird, the bird of birds, birds of the open air. A loaf of bread should speak of reapers, bakers, mills and wheatfields, so that one ingests the world, is nourished by labors and landscapes, not by bread alone. (The supermarket loaf would speak of pesticides and factories, processes that don't correspond to the mythologies and emblems that organize our world.) What complicates the sense of loss is that what is now lost is largely what was absent – what is present has become silent.

Rebecca Solnit, 'Landscapes of Emergency' in Ann Hamilton (University of Washington, 1992) p. 43