KASSEL, GERMANY.- Costing $11 million and occupying five huge sites here, Documenta 11 is the biggest, most expensive version yet of this mega-survey of contemporary art, to which, improbably, more than half a million people flock every five years. This happens to be the most politically oriented Documenta, too, even more than the last one, in 1997. Okwui Enwezor, 39, the Nigerian-born director chosen to put the show together, has delivered more or less what he has promised for the last few years: a global, multigenerational exhibition with works by some unfamiliar names and by international collectives of artists. The result is more about social and economic evangelism than anything else, precisely as he intended. In the catalog Mr. Enwezor, writes, "the exhibition counterpoises the supposed purity and autonomy of the art object against the rethinking of modernity based on ideas of transculturality and extraterritoriality." Social documentaries abound: videos, texts and photographs of railroad laborers in Moldavia, of earthquake damage in Japan, of toxic dump reclamation projects in the United States. All sincere, on the whole not too preachy, thankfully, and occasionally engrossing. The show’s goal, Mr. Enwezor has said, is knowledge through art (one artist described the works here as "epistemological machines”).