Of Mechs and Men : TIDES OF LIGHT <i> by Gregory Benford (Bantam Spectra/ Bantam Books: $17.95; 336 pp.; 0-553-05322-1) </i>

Science-fiction author Gregory Benford writes some of the very best of the so-called “hard� stuff. He knows his science and his scientists--he is one himself, a professor of physics at UC Irvine--and if the theories and gadgets in his stories seem as important as the people, that is wholly appropriate, for the collision of living with nonliving intelligence is Benford’s great theme.

“Tides of Light� is one of a series of novels chronicling the exploits of the human Family Bishop in their unending battle against the evil “mechs,� an ancient race of intelligent machines that have infested the center of the Galaxy. Herein the Bishops and their leader, Cap’n Killeen, undergo further extraordinary adventures; in one virtuoso descriptive sequence, Benford propels his hero right through the center of a planet, which has been cored like an apple by aliens wielding a fearsome, planet-cutting “cosmic string.� In the end, through pluck (and perhaps too much coincidence-straining luck), Killeen and most of his little band of relatives live on to fight another day.

Benford is a hard-working, an inventive, and, above all, a generous writer. He really wants us to know what it might feel like to have computer chips embedded in our spines, each of which holds the memories of one of our ancestors, all of which clamor for our attention because only through our consciousness can they experience continued life. He really wants us to know what it might be like to be a “cyber,� half machine, half giant bug, enmeshed in the political struggles of an anthill as big as a planet.

And Benford really wants us to understand the ontogeny of a being that could live in the vacuum of space by feeding upon comets and asteroids, growing over eons from a tiny seed to a creature one-third the diameter of the Earth before scattering its own seed to the stellar winds. This “Skysower� is tangential to Benford’s story but crucial to his deeper purpose, which is to breathe fictional life into dry theory--in this instance, into computer scientist Marvin Minsky’s notions of the “society of mind� that may underlie natural and artificial intelligence. For this kind of responsible speculation, dedicated fans have elevated Benford to a position in the science fiction pantheon not far below that of the late Robert A. Heinlein, the dean of hard science fiction.

“Tides of Light� shares an imaginary universe with many of Benford’s earlier works, and it is a grim future history indeed, the saga of a Galaxy teeming with diabolical machines whose only apparent purpose is to wipe out all living things. Coming from a scientist who has been an outspoken supporter of our former President’s “Star Wars� strategic defense program--the ultimate in technological optimism--Benford’s sour opinion of machine motivation is not encouraging.

Nor is his opinion of human nature much more cheerful. Benford advances his plot by unremitting confrontation, from all-out war to philosophical disputation to office politics; indeed, sometimes it seems rather as if the universe were a vast chicken coop and the sole purpose of intelligence (natural and artificial) were to determine the pecking order. Thus the novel’s central human relationship, Killeen’s love for his son, is described chiefly in terms of the Cap’n’s efforts to discipline the rebellious lad. Nevertheless the bond between father and son is persuasively rendered, a measure of Benford’s feeling for his characters.

But the non-fan will find Benford rough going. Sci-fi jargon abounds; moreover, Benford is an avowed admirer of William Faulkner--too bad, considering that Faulknerian prose is a writhing snake that Faulker himself could not always keep a grip on--and his prose is to minimalism as ultraviolet is to infrared: “It coiled, clotted scintillant ridges working with snakelike torpor, and then burst into luridly tortured fragments,� Benford writes, describing what is after all just a cloud of gas.

By the conclusion of “Tides of Light,� Benford has effected a reconciliation between two antagonistic, machine-dependent races (one of them human), and has hinted that the evil “mechs� themselves, if hardly benign, may be tools of some higher good. Could this outlook be growing rosier in these kinder and gentler days? No matter; even in a bad mood, Benford gives hard science fiction fans a good read.