As far as I can tell, the essay has considerable intellectual overlap with his most recent book, Hiding in the Mirror : The Mysterious Allure of Extra Dimensions, from Plato to String Theory and Beyond, but is focused on the difference between science and religion, even when dealing with the most abstract, currently untested aspects of our universe.
Much of the essay is spent setting up a comparison between intelligent design (or creationism) and string theory (and, more generally, the idea of extra dimensions), which is sure to drive some of my colleagues crazy. Krauss is certainly critical of what he sees as the blind faith of many scientists pursuing string theory as the ultimate theory of physics. Nevertheless, he stops short of claiming a complete equivalence, conceding
Whatever one thinks about all of these ruminations about hidden realities, there is an important difference – at least I hope there is – between the scientists who currently speculate about extra dimensions and those whose beliefs cause them to insist that life can only be understood by going beyond the confines of the natural world.
Scientists know that without experimental vindication their proposals are likely to wither. Moreover, a single definitive “null experiment,” like the Michelson-Morley experiment in 1887 that dispensed with the long-sought-after ether, could sweep away the whole idea.
Religious belief that the universe is the handiwork of an all-powerful being is not subject to refutation.
Given Lawrence’s clear suspicions about the worth of various activities in contemporary theoretical physics, I’m very pleased to see him using his remarkably high profile to make it clear to the public that, even in its most esoteric aspects, science is fundamentally distinct from religion. He may find certain research directions to be wild goose chases, but it is the possibility of unequivocally proving that they are such that makes them science. Intelligent Design, and the religious ideas underpinning it, cannot make this claim.
Even though this essay is strongly pro-science, I suspect the comments on extra dimensions and string theory to guarantee that tomorrow it will be the topic of much conversation, some heated, in physics departments and some corners of the blogosphere.