'If a tree is seen growing on an island, which do you suppose came first? It is natural (and usually correct) to assume that the island provided the fertile soil in which a lucky seed came to rest. Mangrove forests, however, constitute a revealing exception to this general rule. The Mangrove grows from a floating seed which establishes itself in the water, rooting in shallow mud flats. The seedling sends complex vertical roots through the surface of the water, culminating in what looks to all intents and purposes like a small tree posing on stilts. The complex system of aerial roots, however, soon traps floating soil, weed and debris. After a time, the accumulation of trapped matter forms a small island. As more time passes, the island grows larger and larger. A growing mass of such islands can eventually merge, effectively extending the shoreline out to the trees! Throughout this process, and despite our prior intuitions, it is the land which is progressively built by the trees.
Something like the Mangrove effect, I suspect, is operative in some species of human thought. It is natural to suppose that words are always rooted in the fertile soil of pre-existing thoughts. But sometimes, at least, the influence seems to run in the other direction. A simple example is poetry. In constructing a poem, we do not simply use words to express thoughts. Rather, it is often the properties which of the words (their structure and cadence) which determine the thoughts that the poem comes to express. A similar partial reversal can occur during the construction of complex texts and arguments. By writing down our ideas we generate a trace in a format which opens up a range of new possibilities. We can then inspect and re- inspect the same ideas, coming at them from many different angles and in many different frames of mind. We can hold the original ideas steady so that we may judge them, and safely experiment with subtle alterations. We can store them in ways which allow us to compare and combine them with other complexes of ideas in ways which would quickly defeat the un-augmented imagination. In these ways (...) the real properties of physical text transform the space of possible thoughts.'