  Marc Lange (2011) does however propose a counterexample, arising from the “purely formal” nature of Williams’ argument. Should it not apply equally to “grue” as to “green”? Objects are grue if they are green up to some future point in time, and blue thereafter. The problem is to show that our sample, to date, of green things is not a sample of things actually grue. (Williams’s own views on the grue problem are given in his “How Reality is Reasonable” in (2018)).