From Berenice Abbott:
Let us first say what photography is not. A photograph is not a painting, a poem, a symphony, a dance. It is not just a pretty picture, not an exercise in contortionist techniques and sheer print quality. It is or should be a significant document, a penetrating statement, which can be described in a very simple term – selectivity.
To define selection, one may say that it should be focused on the kind of subject matter which hits you hard with its impact and excites your imagination to the extent that you are forced to take it. Pictures are wasted unless the motive power which impelled you to action is strong and stirring. The motives or points of view are bound to differ with each photographer, and herein lies the important difference which separates one approach from another. Selection of proper picture content comes from a fine union of trained eye and imaginative mind.