"The Revolution That Didn’t Happen" by Steven Weinberg, in The New York Review of Books (Oct. 8, 1998), 1755 Broadway, 5th fl., New York, N.Y. 10019–3780.

In Thomas Kuhn’s theory of scientific revolutions, postmodernist critics of science have found the perfect paradigm. Too bad for them that Kuhn’s radical notions are "quite wrong," according to Weinberg, a Nobel Prize-winning physicist at the University of Texas at Austin.

In his 1962 book The Structure of Scientific Revolutions, Kuhn (1922-96) described the history of science as cyclic: periods of "normal science," in which a particular consensus view ("paradigm") prevails, alternate with revolutionary times that give birth to a new consensus. In Kuhn’s famous phrase, the paradigm shifts. Thus, Newtonian physics, which had gained wide acceptance in the 18th century, was supplanted by the theory of relativity in the early 20th. So great is the gulf between successive paradigms, Kuhn maintained, that scientists adhering to the new model find it all but impossible to understand what their predecessors could have been thinking. And since there is no common standard by which to judge the respective theories, a theory can be called "true" or "false" only within the context of a given paradigm. Science progresses, Kuhn believed, in much the way that Darwinian evolution does—but not, he maintained, toward objective truth. Since all past scientific paradigms had proven false, the current one was bound to give way, too. All this, of course, is catnip to the postmodernist critics who have lately insisted that scientific theories have no more intrinsic validity than, say, astrology or shamanism.

But Kuhn was mistaken in thinking that after a paradigm shift, scientists cannot understand the science that went before, Weinberg points out: "In educating new physicists the first thing that we teach them is still good old Newtonian mechanics, and they never forget how to think in Newtonian terms, even after they learn about Einstein’s theory of relativity." Kuhn was also wrong, Weinberg says, in maintaining that the revo-