EDITORS’ INTRODUCTION

Although the authors are both on the side of science, they have not always agreed about the best ways to oppose religiously motivated threats to scientific practice or instruction. Krauss, a leading physicist, frequently steps into the public spotlight to argue in favor of retaining evolutionary theory in school science curricula and keeping pseudoscientific variants of creationism out of them. An open letter he sent to Pope Benedict XVI in 2005, urging the pontiff not to build new walls between science and faith, led the Vatican to reaffirm the Catholic Church’s acceptance of natural selection as a valid scientific theory. Dawkins, an evolutionary biologist, prolific author and lecturer, is also an eloquent critic of any attempt to undermine scientific reasoning. He has generally shown less interest than Krauss, however, in achieving a peaceful coexistence between science and faith. The title of Dawkins’s best-selling book The God Delusion perhaps best summarizes his opinion of religious belief. These two allies compared notes from the front lines during breaks at a conference devoted to discussing clashes between science and religion held at the Salk Institute for Biological Studies in San Diego late last year. In a dialogue they re-create here, the authors explained their respective tactics for engaging the enemy and tackled some of the questions that face all scientists when deciding whether and how to talk to the faithful about science: Is the goal to teach science or to discredit religion? Can the two worldviews ever enrich one another? Is religion inherently bad? And science can ever test the “God Hypothesis”?(An abridged version of this dialogue appeared in the July 2007 issue of Scientific American)

Krauss: You have cogently argued in The God Delusion that religion is bad science. I would argue, however, that this is particularly inappropriate, and in fact falls into the same trap fallen into by those who push Intelligent Design in science classrooms, as well as those who fund Templeton Foundation grants that attempt to foster scientific evidence for God. I have framed this issue in language that hearkens back to Carl Sagan, who said that absence of evidence is not the same as evidence of absence. Would a world without God necessarily look any different than the world we live in? Most scientists would say no, and thus claim we do not need the God Hypothesis to explain anything about nature. On the other hand one might also ask: Would a world with a God necessarily look any different than the world we live in? People of faith would argue no, and in so doing feel vindicated in their faith. The problem is that both groups are correct, and nothing either can say is likely to influence the other.

Dawkins: I have several times said that a universe with a God would be a very different kind of universe from one without. You have translated this into operational terms, and consequently arrived at the legitimate question of whether the two kinds of universe would look different. Not be different (my question) but look different (your question, where 'look different' can presumably mean any difference, detectable in any way by any of our sense organs or scientific instruments). I agree that yours is an important question, and I agree with you that it might be surprisingly hard to detect, by observation or experiment, whether we live in a god-free universe or a god-endowed one. Nevertheless, I still maintain that there is a cogent sense in which a scientist can discuss the question. There still is a sense in which we can have an interesting and illuminating scientific discussion about whether X is the case, even if we can't demonstrate it one way or the other by observation or experiment. How can I argue this and still claim to be doing science?