  Parsons (1970, reprinted in 1979: 150) points out a related difficulty, the ‘WOOD = FURNITURE’ problem. Suppose that all wood is used to make up furniture and all furniture is made of wood. Then it would seem that the sum of the wood is identical with the sum of the furniture. Therefore, all sentences of the form The wood P and The furniture P are predicted to have the same truth-value, for any predicate P. Yet, it might well be that The furniture is heterogeneous is true, intuitively, while The wood is heterogeneous is false.