Inferences and large dosages of imagination actually have allowed the construction of a far more adequate understanding of the cosmic and human past than earlier generations achieved. I believe that this is the central intellectual accomplishment of the twentieth century. Innumerable cosmologists, physicists, mathematicians, anthropologists, sociologists, historians, ecologists, ethologists, and other specialists have played their part; a few swashbuckling intellects led the way, and the outlines of an evolutionary worldview, uniting natural and human history, has begun to emerge. It may be convincing for generations to come-or again may not.