John Hodgson replies:

John Fagan complains that Nature Biotechnology was inaccurate in describing the limitations of Genetic ID's (and other companies) PCR-based tests for the presence of specific DNA sequences in food. It is possible that the information was inaccurate, but it did come directly from the operations manager at Genetic ID, John McCullough, to whom our reporter spoke directly by telephone. His questions to McCullough were highly specific and the answers unambiguous. I am confident that our reporting is faithful.

John Fagan ends by calling Dan Glickman to the witness stand in his defense. Far from stepping back from agricultural biotechnology as Fagan implies, Glickman was challenging those in the research community to recognize that public opinion and market research were integral parts of product development. He was reminding them not to assume that everything that springs from science and technology will find public favor. He was backing "public information and consumer education efforts that address concerns and allay fears." In the parts of the speech that Fagan regarded as excisable introns, the secretary of agriculture made it clear that he believes that "farmers and consumers will eventually come to see economic and health benefits of these products," and that the UK grocery chains who want to eliminate GM ingredients "need a little educating."

In the current climate of suspicion, tests that detect GM ingredients in food can indeed provide retailers with a competitive advantage in their markets. The tests are dressed with an aura of scientific worthiness; they are lab-based, have controls, and have stated levels of stringency. Their fundamental flaw, however, lies in their scientific emptiness. They demonstrate that GM ingredients can be detected (or not). But the big question still remains: "To what end?"