Astronomer Jastrow considers Loom the third work in a trilogy, after Red Giants and White Dwarfs and Until the Sun Dies. Together, they progress from popular astronomy and cosmology to futurology--here seen in terms of the co-evolution of man and machines. They also move from received wisdom to speculation to the very iffy prospect, now, of a not-too-distant symbiosis between man and artificial intelligence: together human and machine brains will pursue contact with older, wiser civilizations which have already achieved man/machine union. What is the basis for such baroque conjecture? Well, Jastrow--like Carl Sagan, like numerous molecular biologists--has been reading about the brain and, tantalized, wants to add his pittance. The result is an ambitious culling from the neuroscience and paleontology literature--but a culling as selective and subjective as Sagan's. Both men lean toward the brain-computer paradigm, seeing the brain as a gloriously miniaturized lump of complex circuitry that operates with enviable flexibility. Both also accept newfangled versions of the classic tripartite brain--the kind of 19th century ""faculty"" psychology that invariable pits a superior reasoning or cognitive faculty against the old mammal or reptile that lurks within. While Jastrow declares himself an agnostic, he (more than Sagan) leans toward a purposive view of evolution, an onward, upward progression propelled by slow, inexorable Darwinian selection. Both in large and small details, Loom presents as fact many points now being argued on the pages of the professional paleontology and neuroscience journals. (Even Hubel and Wiesel's elegant work on the physiology of vision--for which they have just won the Nobel prize--is blurred in Jastrow's reading of it.) True, Jastrow's abilities at condensation and simplification are amply demonstrated in the text, as is his ability to rouse the reader to the importance and excitement of what he's saying. One can only wish for more facts and less fancy.