Modal features of quantities are taken up in this chapter. Talk of atomic number as the essence of something, unclear exactly what, is put aside in favour of pursuing Paneth’s more fruitful distinction between elements as simple and as basic, leading to a discussion of how resilient being the same element is to possible changes in states of combination. The chapter goes on to develop the idea of it being possible for a quantity to be such-and-such, which is introduced to deal with claims difficult to capture with conventional sentential modal operators. This leads to replacing the treatment of modality in terms of modal operators by the explicit quantification over possible states to achieve appropriate expressive power. Incorporation of possible processes is a natural development, linking up with the discussion in Chap. 8 .