You find a rock. It looks like an ordinary piece of flint, broken and rough. On a part of it is a patina whose soft grey color contrasts with the shiny brownish surfaces of conchoidal fracture. You could have found this rock in nearly any kind of an environment almost anyplace in the world. There is nothing distinctive about it.
You hand this same piece of rock to a colleague and ask what he can make of it. He considers it soberly before he says, “You know, that could be an artifact.” There springs to mind then a picture of a primitive man, squatting barefoot before a fire warming his hands. The firelight casts his shadow against the cliff below which he crouches.
The difference between the reaction before and after the passing thought that this might indeed be the tool of ancient man is the difference between mild disinterest and a kaleidoscope of mental pictures. This difference reflects differences in the associations of thoughts.
The present essay is concerned with how associations are used in geologic reasoning, and then with certain philosophic considerations which seem to be influencing the methodology and direction of geomorphology.