It's a recurring question. Whether there will ever be a definitive answer is dubious. But in the case of Richard Avedon there isn't much of a problem. It's both. Whether it is a glamour girl of the 1950's in a glamorous ballgown of the period, or portraits of real people which somehow acquire a stylish demeanor, the difference between fashion and art is diminished.
The question also comes up with the work of Geoffrey Beene who didn't aspire to making art, just clothes. Yet he cared so much about line and fabric that his work often approached the dignity of art.
Both the photographer and the designer died in the past week, leaving a vacuum that would not be filled with lesser lights. In both cases, it was a case of passion: doing the job so well it could not be improved upon. And of course, there was the talent.
There is no lack of talent today among both designers and photographers. But seeing as clearly as both men did is a special gift. It is not necessary that every dress and every photograph be a work of art. But at their best, the dress and the picture of the dress transcends itself. It becomes something else, something beautiful and permanent. It has a right to be called art.
So the question whether fashion is art cannot easily be resolved. In their highest forms, the distinction is not significant.