 A fourth sub-type of negative thought experiments are “counter thought experiments” (see Brown 2007). Norton very usefully introduces a related idea: “thought-experiment/anti-thought-experiment pairs” (see Norton 2004, pp. 45–49). Above, we have already encountered this subtype in our discussion of Lucretius’ spear-thought experiment, and with Dennett’s reply to Jackson’s much discussed Mary the colour scientist thought experiment. Here we would like to add one more example, namely Mach’s counter thought experiment against absolute space. In his Principia Mathematica, Newton offers a pair of thought experiments as evidence for absolute space. One is the bucket with water climbing the wall, the other is a pair of spheres joined by a cord that maintained its tension in otherwise empty space. The explanation for these phenomena, argues Newton, is absolute space: the bucket and the joined spheres are rotating with respect to space itself. In response, Mach modifies the scenario and argues, contra Newton, that the two spheres would move toward one another thanks to the tension in the cord, and if we rotated a very thick, massive ring around a stationary bucket, we would see the water climb the bucket wall. (For further discussion of Mach’s counter thought experiment to Newton’s see Kühne 2006, pp. 191–202). In short, the point of Mach’s counter thought experiments is to describe the phenomena of the thought experiments’ scenarios differently, that is, to declare that different things would happen. Mach’s counter thought experiment undermines our confidence in Newton’s. Absolute space might be a plausible explanation of the phenomena in Newton’s thought experiments, but now, in light of Mach’s counter thought experiment, we’re not so sure of the phenomena itself and thus of the idea of absolute space.