 Boyle was arguing specifically against a Jesuit scientist, Franciscus Linus, who claimed, not that ordinary atmospheric air does not have any pressure (a spring), but that its pressure was not sufficiently powerful for it to do all the things it does in fact do. So Boyle decided on an experiment to show the way in which, as we would say, the pressure and the volume of the air vary, when the air is, in Boyle’s words, either ‘compressed or dilated.’