Sir

In his review of my book Yes, We Have No Neutrons, Walter Gratzer adopts a dismissive tone that seems to have more to do with my having chosen examples of science-gone-wrong that were not to his particular taste than with the very substantive issues involved (Nature 388, 36; 1997). It is most instructive to watch how research goes off the rails when scientists who think they have made an earth-shattering discovery forget the elements of good method. The frailties of ego undermine the discipline needed to make the very tests that will disprove the hypothesis.

In the case of the search for extraterrestrial intelligence (SETI) the hypothesis is nonfalsifiable. This does not make me a student of Karl Popper, but someone who believes that the SETI experiment is only half an experiment, at best. If aliens are sending us messages, the SETI programme is (or was) superbly equipped, we think, to pluck them from the sky. But if aliens are not sending us messages, there is no way the programme can rule out this possibility. Drake and company would merely tighten the bandwidth, add more billions of processors, search more of the sky more of the time and so on. There is no stopping rule: no test for the non-existence of such messages.

Gratzer is incorrect when he claims that receipt of such messages would prove me wrong. Although the book has a certain amount of fun with the idea of what such messages might be like, it makes no claim that they are not, in fact, being sent. It merely asserts that if no recipes for fantastic new discoveries are bathing the planet, we have no way to find out.

The review ends on a profoundly discouraging note in which Gratzer feels compelled to quote Werfel: “For those who believe, no explanation is necessary, while for those who do not believe, no explanation is possible.”

Has the general readership already hardened into two camps on each of the eight examples of “bad science” explored in the book? I think not. I hope not. Is this a general assertion about the uselessness of making any distinction between good and bad science? One would like to say “science” and “non-science” in place of these adjectives, but, as Gratzer points out, just about everything is called “science” these days.