MR. WILLIAMSON points out that in most ordinary language the meaning of a sentence depends on its context only to a trifling or zero degree. Nevertheless, the recognition that the dependence is latent may be worth making. We all know how much Shannon and Wiener contributed by their recognition that the quantity of information in a message is a function both of it and of the unsent messages. They showed that a coherent theory can be developed only when the set of messages is regarded as a whole. It may be that a theory of meaning similarly must be based on consideration of the whole set. In such a theory, the sentence the meaning of which depends on context to only zero degree would be regarded as a special (though common) case, degenerate in the way that ‘still air’ corresponds to the wind that blows at 0 miles per hour.