Contributed by Jonathan Stevenson / There are certainly strong generational reasons for the Whitney to mount “Andy Warhol – From A to B and Back Again,” its penetrating current retrospective. It goes almost without saying that Warhol changed art history by melding the commercial and the “fine,” and, in his energized aesthetic embrace of the whole world (especially New York), by irreversibly expanding the horizons of art and substantially advancing its conceptual dimension. At the same time, it’s tempting to question whether he has more particular contemporary relevance – or at least whether today his work resonates positively or constructively.