 Now let us introduce another predicate less familiar than “green”. It is the predicate “grue” and it applies to all things examined before \(t\) just in case they are green but to other things just in case they are blue. Then at time \(t\) we have, for each evidence statement asserting that a given emerald is green, a parallel evidence statement asserting that emerald is grue. The question is whether we should conjecture that all emeralds are green rather than that all emeralds are grue when we obtain a sample of green emeralds examined before time \(t\), and if so, why.