In the course of an extraordinary series of lectures here a week ago, Evan Koslow advanced in mind-numbing terms the proposition that if you could somehow condition the American public to make the right kind of civil defense effort, the United States could survive a knock-down, drag-out nuclear war. Koslow is a bright young engineer who specializes in these matters. You could take comfort that he is dealing in well-hedged hypotheses.

Or you could until the arrival of a new book by Los Angeles Times reporter Robert Scheer. His proposition is that Koslow's flight of fancy is the very foundation of the Reagan administration's nuclear strategy. His first paragraph asserts the existence of a "secret plan for the United States to prevail in a protracted nuclear war." Ronald Reagan approved the plan earlier this year, Scheer write, and backed it up by sending Congress a civil defense program that would cost $4.3 billion over seven years.

Underlying this effort to "harden" the populace, natural resources, and the command and control of "nuclear war fighting" are assumptions shared at the highest levels of the administration: that the Soviets think a nuclear war is winnable and are making preparations; that the proper purpose of U.S. foreign policy is not just to contain the Soviet system; and that the United States can only press this objective by being willing to risk a nuclear confrontation. That's Scheer's view, buttressed by "hundreds of hours" of interviews with Reagan, George Bush, arms control negotiator Eugene Rostow, Assistant Secretary of Defense Richard Perle, Assistant Secretary of State Richard Burt and a host of other well- placed participants in the Reagan administration's foreign policy-making.

It is impossible, of course, to verify all of Scheer's impressive documentation. But he adds new substance to the strong suspicion that Ronald Reagan has attracted to his strategic councils a collection of certifiable Dr. Strangeloves -- right-wing ideologues who share a conviction, central to all the rest of their designs, that a nuclear war can be "won."

The title of Scheer's book, "With Enough Shovels: Reagan, Bush and Nuclear War," is taken from a passage in an interview with Thomas K. ("T.K.") Jones, deputy undersecretary of defense for research and engineering, strategic and theater nuclear forces. Jones' message for America is: "Dig a hole, cover it with a couple of doors and then throw three feet of dirt on top. . . . It's the dirt that does it. . . . . If there are enough shovels to go around, everybody's going to make it."

Except that, if Koslow is anything like as expert on the subject as he seems to be, not nearly everybody is going to make it. That hole that T.K. Jones would have us dig is a death trap, according to Koslow -- unless it's well ventilated.

But a much bigger problem would be persuading people to take the necessary precautions -- like shoveling a couple of feet of dirt on the living room floor to increase protection for those taking refuge in the basement below.

For every upbeat aspect, Koslow freely admits to a caveat. The United States, with its farm price-support program, is way ahead of the Soviets in the amount of foodstuffs stored away and available in the aftermath of a nuclear war. But distribution would be a major hurdle. Most vehicles might be operational, but fuel to move them might not be available.

If you are five miles away from a detonation, "blast is no longer your problem," but fallout is. Even those sheltered survivors who escape the effects of fallout will find themselves confronting the effects of whatever damage has been done to the Earth's ozone shield. The resulting breakthrough of ultraviolet light could make food crops far more vulnerable to this aftereffect than to fallout.

"T.K. Jones is not completely out of his mind" on the value of a few shovelfuls of dirt, Koslow declares. But "you may come out and find that your culture has been destroyed, you are unable to get a job, and it's not possible to come together as a social and economic group anymore."

Listening to Koslow, you are convinced that civil defense is at best a dubious proposition. No program either exists or is likely to be undertaken on a big scale. Reading Scheer, you are persuaded that Ronald Reagan and his nuclear strategists have not even begun to take this into their calculations.

One conclusion seems inescapable. If administration officials ever started talking publicly the way they would have to talk in order to condition public opinion for "winning" a nuclear war, they would turn the relatively unfocused fear behind the drive for a "nuclear freeze" into a national nuclear psychosis.