The unending script, the code of conduct for scientific argument according to which Montague and Capulet may continue their debate indefinitely, is provided by the methodological precept that I call the iron rule of explanation. What the rule says is simple enough: it directs scientists to resolve their differences of opinion by conducting empirical tests rather than by shouting or fighting or philosophizing or moralizing or marrying or calling on a higher power. That is all; it makes no attempt to interpret the evidence, to decide winners and losers.
