The concept of electrical conductivity, or, as initially coined by Stephen Gray , ‘electrical communication’, has always been assigned an important role in the history of electrical research. Some thirty-five years after Gray's ‘electrical communication’ acquired wide attention, Priestley employed the concept of conductivity to define physical reality, thus giving a privileged position to the science he himself endeavoured to cultivate. As he argued in the introduction to The History and Present State of Electricity , ‘the electrical fluid is no (...) local, or occasional agent in the theatre of the world. Late discoveries show that its presence and effects are every where … It is not, like magnetism, confined to one kind of bodies, but every thing we know is a conductor or nonconductor of electricity’. Contemporary historians, for example, Heilbron, Home and Hackmann, link the concept of conductivity to a radical transformation of electrical research which pertained to its mode of organization and the definition of its subject-matter, and which culminated in its emergence as a distinctive branch of eighteenth-century ‘experimental philosophy’. (shrink)