Abstract
I highlight a category of experiment-what I am calling 'demonstrations'-that differs in justificatory mode and argumentative role from the more familiar 'crucial tests'. 'Tests' are constructed such that alternative results are equally and symmetrically informative; they help discriminate between alternative solutions within a problem-field, where questions are shared. 'Demonstrations' are notably asymmetrical (for example, "failures" are often not telling), yet they are effective, if not "crucial," in interparadigm dispute, to legitimate questions themselves. The Ox-Phos Controversy in bioenergetics serves as an integral case study.