Gruesome Counterfactuals

One of the most popular answers to the grue puzzle appeals to counterfactual dependence. An observed green emerald is grue. But while it still would have been green even if unobserved, if unobserved it would not have been grue. Because of this, or something like it, we can project ‘green’ but not ‘grue’ to the unobserved emeralds. Counterfactual theories have been offered by Frank Jackson and Peter Godfrey-Smith, among others. But there is a worry that all counterfactual approaches to grue fail for the same reason—counterfactual symmetry. The grue theorist can endorse symmetrical counterfactuals: an observed green emerald would have been grue but not green if unobserved. It then seems that counterfactual responses to grue beg the question. Here I argue that there are two ways to understand this challenge and that they both fail, but for different reasons. I close by drawing some general lessons about philosophical fair play regarding the twentieth century’s many broadly semantic, broadly skeptical challenges—grue, quus, gavagai, and the like

Counterfactual conditional · Counterfactual thinking · Criticism · Philosophy of science · Skepticism · Worry · Epistemology, Ethics, and Metaphysics · Philosophy and History of Science · Philosophy and Theoretical Science