Moore is also remembered for drawing attention to the peculiar inconsistency involved in uttering a sentence such as "It is raining but I do not believe it is raining."—a puzzle which is now commonly called "Moore's paradox." The puzzle arises because it seems impossible for anyone to consistently assert such a sentence; but there doesn't seem to be any logical contradiction between "It is raining" and "I don't believe that it is raining." because the former is a statement about the weather and the latter a statement about a person's belief about the weather, and it is perfectly logically possible that it may rain whilst a person does not believe that it is raining.
In addition to Moore's own work on the paradox, the puzzle also inspired a great deal of work by Ludwig Wittgenstein, who described the paradox as the most impressive philosophical insight that Moore had ever introduced. It is said that when Wittgenstein first heard this paradox one evening (which Moore had earlier stated in a lecture), he rushed round to Moore's lodgings, got him out of bed and insisted that Moore repeat the entire lecture to him.