In 1978 Edwin Land, co-founder of Polaroid, published a letter in the company's annual report. I believe it speaks volumes to a photographer about photography. Thus, I give it a permanent place in my mind and on my website.

The most extraordinary of man’s artifacts in the reconstruction of reality is the black and white image comprising, of course, a series of grays. It can be shown that in seeing color, objects are separated out from each other by the preferential efficiency of the surface of one object or another for reflecting light of one wavelength or another and that this preferentially remains intact irrespective of the variation in time and place of the illumination of the object from the world around it. Black and white photography generates, as it were, a substitute world: light of the same wavelength composition comes to the eye from any part of the scene. This preferentially for reflecting at different wavelengths (colors) is absent and cannot be used to designate objects. Rather only the difference from object to object in the efficiency for reflecting a uniform mixture of wavelengths can be used.
Here comes the miracle. The enormous variations in illumination of the objects by the world around them have led to enormous variations in the amount of light reaching one object or another in a random way, so that portions of the photograph delineating dark objects may send to the eye more light than portions of the photograph delineating white objects. In short, the photograph is two entirely different kinds of report transmitted to us by what appear to be mixed languages, the language for delineating objects and the language for displaying illumination.
There have not been many great photographers in history, but the great ones usually turn out to be masters of the vocabulary of these two utterly different languages in black and white photography. For most would-be photographers these languages are mixed together and never disentangle, like the babble of voices at a cocktail party. The breathtaking competence of the great photographer is to cause the object of his choice to be revealed with symphonic grandeur, meticulous in detail, majestic in illumination.

-       Dr. Edwin Land, Chairman’s Letter 1978 Polaroid Annual Report