The debate over recombinant DNA research is a unique event, perhaps a turning point, in the history of science. For the first time in modern history there has been widespread public discussion about whether and how a promising though potentially dangerous line of research shall be pursued. At root the debate is a moral debate and, like most such debates, requires proper assessment of the facts at crucial stages in the argument. A good deal of the controversy over recombinant DNA research arises because some of the facts simply are not yet known. There are many empirical questions we would like to have answered before coming to a decision—questions about the reliability of proposed containment facilities, about the viability of enfeebled strains of Escherichia coli, about the ways in which pathogenic organisms do their unwelcome work, and much more. But all decisions cannot wait until the facts are available; some must be made now. It is to be expected that people with different hunches about what the facts will turn out to be will urge different decisions on how recombinant DNA research should be regulated. However, differing expectations about the facts have not been the only fuel for controversy. A significant part of the current debate can be traced to differences over moral principles. Also, unfortunately, there has been much unnecessary debate generated by careless moral reasoning and a failure to attend to the logical structure of some of the moral arguments that have been advanced.