ABSTRACT
This chapter considers that chemical substances or structures cannot be strongly emergent because their being so would entail the possibility of downward causation. In the case of chemistry, the scientific pedigree of instrumentalism about structure is quite as long as that of structural explanation itself. Chemistry supplied the atoms, and initially the physicists took some persuading of their existence: physicists came late to chemical atomism. One reason why many philosophers reject the idea that there can be any strong emergence in chemistry is that they think that the reducibility of chemical entities and properties to physical entities and properties, or their identity with physical entities and properties, has been established through such theoretical identities as "water is H2O". Since chemists regard the electrical conductivity they measure as a property of pure water, it seems gratuitous for the philosophers to interpret it instead as a property of an aqueous solution of water's ionic dissociation products.
